CoChat
Sign Up
Cited by 898SARS-CoV-2 and COVID-19 ResearchCOVID-19 Clinical Research StudiesCOVID-19 epidemiological studies

The DOI matches its Crossref record; 32 of the 32 references it cites were found in a registry or an index; 16 of the 19 sources its claims cite were checked for support.

Efficacy and safety of an inactivated whole-virion SARS-CoV-2 vaccine (CoronaVac): interim results of a double-blind, randomised, placebo-controlled, phase 3 trial in Turkey

Open access
Tanriover, Mine Durusu, Doğanay, Hamdi Levent, Akova, Murat, Güner, Hatice Rahmet, Azap, Alpay, Akhan, Sıla, Köse, Şükran, Erdinç, Fatma Şebnem, Akalın, Emin Halis, Tabak, Ömer Fehmi, Pullukçu, Hüsnü, Batum, Özgür, Şimşek Yavuz, Serap, Turhan, Özge, Yıldırmak, Mustafa Taner, Köksal, İftihar, Taşova, Yeşim, Korten, Volkan, Yılmaz, Gürdal, Çelen, Mustafa Kemal, Altın, Sedat, Çelik, İlhami, Bayındır, Yaşar, Karaoğlan, İlkay, Yılmaz, Aydın, Özkul, Aykut, Gür, Hazal, Unal, Serhat, Kayaaslan, Bircan, Hasanoğlu, İmran, Dalkıran, Ayça, Aydos, Ömer, Çınar, Güle, Akdemir-Kalkan, İrem, İnkaya, Ahmet Çağkan, Aydin, Mehtap, Çakir, Hatice, Yıldız, Jale, Kocabıyık, Özenir, Arslan, Sonay, Nallı, Bayram, Demir, Ömer, Singil, Sarp, Ataman-Hatipoğlu, Çiğdem, Tuncer-Ertem, Günay, Kınıklı, Sami, Önal, Uğur, Mete, Bilgül, Dalgan, Gözde, Taşbakan, Meltem, Yamazhan, Tansu, Kömürcüoğlu, Berna, Yalnız, Enver, Benli, Aysun, Keskin-Sarıtaş, Çağla, Ertosun, Mustafa Gökhan, Özkan, Özlenen, Emre, Salih, Arıca, Seçil, Kuşçu, Ferit, Candevir, Aslıhan, Ertürk-Şengel, Buket, Ayvaz, Fadime, Aksoy, Firdevs, Mermutluoğlu, Çiğdem, Demir, Yakup, Günlüoğlu, Gülşah, Tural-Önür, Seda, Kılıç-Toker, Ayşin, Eren, Esma, Otlu, Barış, Mete, Ayşe Özlem, Koçak, Kübra, Ateş, Hale, Koca-Kalkan, İlkay, Aksu, Kurtuluş·2021·The Lancet
DOI 10.1016/s0140-6736(21)01429-xPMC PMC8266301
Open this paper in CoChat — free accountOpen PDF

Abstract

Background CoronaVac, an inactivated whole-virion SARS-CoV-2 vaccine, has been shown to be well tolerated with a good safety profile in individuals aged 18 years and older in phase 1/2 trials, and provided a good humoral response against SARS-CoV-2. We present the interim efficacy and safety results of a phase 3 clinical trial of CoronaVac in Turkey. Methods This was a double-blind, randomised, placebo-controlled phase 3 trial. Volunteers aged 18-59 years with no history of COVID-19 and with negative PCR and antibody test results for SARS-CoV-2 were enrolled at 24 centres in Turkey. Exclusion criteria included (but were not limited to) immunosuppressive therapy (including steroids) within the past 6 months, bleeding disorders, asplenia, and receipt of any blood products or immunoglobulins within the past 3 months. The K1 cohort consisted of health-care workers (randomised in a 1:1 ratio), and individuals other than health-care workers were also recruited into the K2 cohort (randomised in a 2:1 ratio) using an interactive web response system. The study vaccine was 3 μg inactivated SARS-CoV-2 virion adsorbed to aluminium hydroxide in a 0·5 mL aqueous suspension. Participants received either vaccine or placebo (consisting of all vaccine components except inactivated virus) intramuscularly on days 0 and 14. The primary efficacy outcome was the prevention of PCR-confirmed symptomatic COVID-19 at least 14 days after the second dose in the per protocol population. Safety analyses were done in the intention-to-treat population. This study is registered with ClinicalTrials.gov (NCT04582344) and is active but no longer recruiting. Findings Among 11 303 volunteers screened between Sept 14, 2020, and Jan 5, 2021, 10 218 were randomly allocated. After exclusion of four participants from the vaccine group because of protocol deviations, the intention-to-treat group consisted of 10 214 participants (6646 [65·1%] in the vaccine group and 3568 [34·9%] in the placebo group) and the per protocol group consisted of 10 029 participants (6559 [65·4%] and 3470 [34·6%]) who received two doses of vaccine or placebo. During a median follow-up period of 43 days (IQR 36-48), nine cases of PCR-confirmed symptomatic COVID-19 were reported in the vaccine group (31·7 cases [14·6-59·3] per 1000 person-years) and 32 cases were reported in the placebo group (192·3 cases [135·7-261·1] per 1000 person-years) 14 days or more after the second dose, yielding a vaccine efficacy of 83·5% (95% CI 65·4-92·1; p<0·0001). The frequencies of any adverse events were 1259 (18·9%) in the vaccine group and 603 (16·9%) in the placebo group (p=0·0108) with no fatalities or grade 4 adverse events. The most common systemic adverse event was fatigue (546 [8·2%] participants in the vaccine group and 248 [7·0%] the placebo group, p=0·0228). Injection-site pain was the most frequent local adverse event (157 [2·4%] in the vaccine group and 40 [1·1%] in the placebo group, p<0·0001). Interpretation CoronaVac has high efficacy against PCR-confirmed symptomatic COVID-19 with a good safety and tolerability profile. Funding Turkish Health Institutes Association.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

In this interim analysis of a double-blind, randomised, placebo-controlled phase 3 trial in Turkey, CoronaVac showed 83·5% efficacy against PCR-confirmed symptomatic COVID-19 at least 14 days after the second dose in adults aged 18–59 years, with no COVID-19 hospitalisations in vaccine recipients. The vaccine had a good safety profile, with no grade 4 adverse events or deaths and low adverse event incidence.

Key findings

  • Among the per protocol population (n=10,029), 41 symptomatic COVID-19 cases occurred ≥14 days after the second dose: 9 in the vaccine group (31·7 cases [14·6–59·3] per 1000 person-years) versus 32 in the placebo group (192·3 cases [135·7–261·1] per 1000 person-years), yielding vaccine efficacy of 83·5% (95% CI 65·4–92·1; p<0·0001).
  • Hospitalisation for COVID-19 occurred in none of the vaccine group and six in the placebo group, giving vaccine efficacy of 100% (20·4–100·0; p=0·0344); there were no fatal COVID-19 cases.
  • Immunogenicity: 880 (89·7%) vaccine recipients versus 19 (4·4%) placebo recipients were seropositive for RBD-specific total antibody (p<0·0001); among selected seropositive vaccine samples (n=387), 356 (92·0%) had SN50 of at least 1/15.
  • Safety: any adverse events occurred in 1259 (18·9%) vaccine recipients versus 603 (16·9%) placebo recipients (p=0·0108); there were no grade 4 adverse events or deaths. The most common systemic adverse event was fatigue (546 [8·2%] vs 248 [7·0%], p=0·0228), and injection-site pain was the most frequent local adverse event (157 [2·4%] vs 40 [1·1%], p<0·0001).

Methods

  • Double-blind, randomised, placebo-controlled phase 3 trial at 24 centres in Turkey. Volunteers aged 18–59 years with no history of COVID-19 and negative PCR and antibody results were enrolled; K1 healthcare workers were randomised 1:1 and K2 participants (community plus healthcare workers) were randomised 2:1. Of 11,303 screened, 10,218 were randomly allocated; the intention-to-treat population was 10,214 and the per protocol population was 10,029.
  • The vaccine was 3 μg inactivated SARS-CoV-2 virion adsorbed to aluminium hydroxide in a 0·5 mL aqueous suspension, given intramuscularly on days 0 and 14; placebo contained all vaccine components except inactivated virus.
  • The primary efficacy outcome was PCR-confirmed symptomatic COVID-19 at least 14 days after the second dose in the per protocol population; safety analyses were done in the intention-to-treat population. Efficacy was calculated using COVID-19-free person-years; median follow-up from randomisation to unmasking was 43 days (IQR 36–48).

Limitations

  • Stated: median follow-up after randomisation to unmasking was 43 days (IQR 36–48), which is very short; long-term protective effects of the two-dose schedule cannot be assessed from this interim analysis.
  • Stated: the study population was relatively young (median age 45 years [IQR 37–51]) and healthy with low chronic disease prevalence and a very low event rate; few participants were hospitalised and the population was at relatively low risk of severe or critical COVID-19, limiting generalisability, especially for severe disease.
  • Stated: the trial used a 14-day interval whereas community immunisation used 28 days; results predate variants of concern, so efficacy against mutant viruses cannot be assessed; the report lacks sequential serum neutralising antibody titres, T-cell response magnitude, and duration of protectivity, and used a semiquantitative immunoassay. The target sample size was not reached because emergency use authorisation and vaccination began during recruitment. Evident from the text: this is an interim analysis, and subgroup efficacy analyses were not designed or powered.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1016/s0140-6736(21)01429-x

Cites

32 of 32 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

16 of 19 cited sources checked · 6 supported · 0 flagged · accuracy not yet measured

  • Premisecitation

    Phase 1/2 trials of CoronaVac in volunteers aged 18-59 years and older than 60 years showed that the vaccine doses and schedules investigated (3 μg or 6 μg, applied 14 days or 28 days apart) all had similar safety and immunogenicity profiles.

    “Phase 1/2 trials of CoronaVac in volunteers aged 18–59 years and older than 60 years showed that the vaccine doses and schedules investigated (3 μg or 6 μg, applied 14 days or 28 days apart) all had similar safety and immunogenicity profiles.20, 21”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites [20] Zhang, 2021, Safety, tolerability, and immunogenicity of an inactivated SARS-CoV-2 vaccine in healthy adults aged 18–59 years: a randomised, double-blind, placebo-controlled, phase 1/2 clinical trial, Lancet Infect Dis source

      Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • cites [21] Wu, 2021, Safety, tolerability, and immunogenicity of an inactivated SARS-CoV-2 vaccine (CoronaVac) in healthy adults aged 60 years and older: a randomised, double-blind, placebo-controlled, phase 1/2 clinical trial, Lancet Infect Dis source

      Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
  • Premisecitation

    The interim phase 3 results of other COVID-19 vaccines have shown efficacies ranging from 62.1% to 95%.

    “The interim phase 3 results of other COVID-19 vaccines have shown efficacies ranging from 62·1% to 95%.24, 25, 26, 27, 28”
    Quote in the paperNot a substantial claim5 of 5 sources checked
    • cites [24] Logunov, 2021, Safety and efficacy of an rAd26 and rAd5 vector-based heterologous prime-boost COVID-19 vaccine: an interim analysis of a randomised controlled phase 3 trial in Russia, Lancet source
    • cites [25] Baden, 2021, Efficacy and safety of the mRNA-1273 SARS-CoV-2 vaccine, N Engl J Med source

      The Statistical Analysis section (p. 4) reports 94.5% efficacy for mRNA-1273 at the first interim analysis, supporting the approximately 95% end of the stated range. This paper does not report a 62.1% efficacy result or establish the full range across COVID-19 vaccines. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
    • cites [26] Polack, 2020, Safety and efficacy of the BNT162b2 mRNA COVID-19 vaccine, N Engl J Med source
    • cites [27] Voysey, 2021, Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK, Lancet source

      Table 2 in the Results reports 62·1% efficacy for standard-dose ChAdOx1 recipients in this interim analysis. The Research in context passage reports 95% for Pfizer/BioNTech, but identifies that figure as coming from a primary analysis, not an interim analysis. Thus the range is supported, but the sentence's 'interim' qualifier does not fit both endpoints. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [28] Sadoff, 2021, Safety and efficacy of single-dose Ad26.COV2.S vaccine against COVID-19, N Engl J Med source

      The Results > Efficacy and Discussion (page unavailable) report efficacy for Ad26.COV2.S, not the interim phase 3 efficacy range for other COVID-19 vaccines. Searches for 62.1%, 95%, and other vaccine trials found no passage in our copy establishing the claimed range. (LLM, conf=0.76)

      Experimental — accuracy not yet measured
  • Findingown data

    Preliminary immunogenicity results revealed that CoronaVac induced anti-receptor-binding domain antibodies in 89.7% of participants.

    “Preliminary immunogenicity results revealed that CoronaVac induced anti-receptor-binding domain antibodies in 89·7% of participants.”
    Quote in the paperNot a substantial claim
  • Findingown data

    No cases of COVID-19 requiring hospitalisation occurred in the study.

    “with no cases of COVID-19 requiring hospitalisation”
    Quote in the paperSubstantial claim
  • Findingown data

    During a median follow-up of 43 days, nine cases of PCR-confirmed symptomatic COVID-19 were reported in the vaccine group.

    “During a median follow-up period of 43 days (IQR 36–48), nine cases of PCR-confirmed symptomatic COVID-19 were reported in the vaccine group”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim. 25
  • It may state two separate claims as one. 35
  • The quote only partly states this claim. 3

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Study design and conductcitation

    The entire study protocol was published previously and is available on the Hacettepe University Vaccine Institute website.

    “The entire study protocol was published previously and is available on the Hacettepe University Vaccine Institute website.10”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [10] Akova, 2021, A randomized, double-blind, placebo-controlled phase III clinical trial to evaluate the efficacy and safety of SARS-CoV-2 vaccine (inactivated, Vero cell): a structured summary of a study protocol for a randomised controlled trial, Trials source

      The Full Protocol section (page not specified) says the complete protocol is attached to this article as Additional file 1 and is accessible from the Trials website. It does not say the protocol was published previously or is available on the Hacettepe University Vaccine Institute website. (LLM, conf=0.88)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    Inactivated SARS-CoV-2 vaccine candidates have shown promising results in preclinical trials.

    “Inactivated SARS-CoV-2 vaccine candidates have shown promising results in preclinical trials.13, 14, 15”
    Quote in the paperNot a substantial claim3 of 3 sources checked
    • cites [13] Gao, 2020, Development of an inactivated vaccine candidate for SARS-CoV-2, Science source
    • cites [14] Wang, 2020, Development of an inactivated vaccine candidate, BBIBP-CorV, with potent protection against SARS-CoV-2, Cell source
    • cites [15] Mohandas, 2021, Immunogenicity and protective efficacy of BBV152, whole virion inactivated SARS-CoV-2 vaccine candidates in the Syrian hamster model, iScience source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Premisecitation

    Disadvantages of inactivated vaccines include limited immunogenicity requiring adjuvants, large quantities of live virus to be handled, and integrity of antigens or epitopes that should be verified.

    “Disadvantages include limited immunogenicity requiring adjuvants to enhance the immune response, large quantities of live virus to be handled, and the integrity of antigens or epitopes that should be verified.8”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [8] Awadasseid, 2021, Current advances in the development of SARS-CoV-2 vaccines, Int J Biol Sci source

      The Safety section (page unavailable) says adjuvants can improve vaccine immunogenicity, and Selection of antigens > Whole-cell antigen says killed-virus vaccines require careful quality assurance. Neither passage says inactivated vaccines have limited immunogenicity requiring adjuvants, require handling large quantities of live virus, or specifically require verification of antigen or epitope integrity. Searches for those terms found no more direct support. (LLM, conf=0.82)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    Considering the production capacity and emergent need for vaccines, the 3 μg dose of CoronaVac has been suggested for efficacy assessment.

    “Considering the production capacity and emergent need for vaccines, the 3 μg dose of CoronaVac has been suggested for efficacy assessment.20”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [20] Zhang, 2021, Safety, tolerability, and immunogenicity of an inactivated SARS-CoV-2 vaccine in healthy adults aged 18–59 years: a randomised, double-blind, placebo-controlled, phase 1/2 clinical trial, Lancet Infect Dis source

  • It may state two separate claims as one.

    Premisecitation

    Higher and more rapidly established efficacies were observed with mRNA-based vaccines.

    “Higher and more rapidly established efficacies were observed with mRNA-based vaccines.25, 26”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites [25] Baden, 2021, Efficacy and safety of the mRNA-1273 SARS-CoV-2 vaccine, N Engl J Med source

      The Efficacy section (p. 9) reports 94.1% efficacy for mRNA-1273 and 95.2% in an analysis starting 14 days after the first dose. The Discussion (p. 11) describes rapid case accrual and compares its high efficacy with influenza-vaccine efficacy, but the paper does not establish that mRNA vaccines achieved efficacy more rapidly than other vaccine types. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
    • cites [26] Polack, 2020, Safety and efficacy of the BNT162b2 mRNA COVID-19 vaccine, N Engl J Med source

      The Discussion (page not provided) reports 95% efficacy for BNT162b2 and describes both early protection after vaccination and a demonstration of efficacy less than 11 months after development began. It does not compare efficacy or the speed of establishing it with other vaccine types, and its findings concern one mRNA vaccine rather than mRNA-based vaccines generally. (LLM, conf=0.86)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Premisecitation

    Gao and colleagues showed that, in mice, rats, and rhesus monkeys, 6 μg CoronaVac induced SARS-CoV-2-specific neutralising antibodies that effectively neutralised ten representative SARS-CoV-2 strains and provided complete protection against SARS-CoV-2 challenge in non-human primates.

    “Gao and colleagues13 showed that, in mice, rats, and rhesus monkeys, 6 μg CoronaVac induced SARS-CoV-2-specific neutralising antibodies that effectively neutralised ten representative SARS-CoV-2 strains and provided complete protection against SARS-CoV-2 challenge in non-human primates.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [13] Gao, 2020, Development of an inactivated vaccine candidate for SARS-CoV-2, Science source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Findingown data

    Among 11,303 volunteers screened, 10,218 were randomly allocated.

    “11 303 volunteers were screened for eligibility, and 10 218 were randomly allocated”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    The per protocol group consisted of 10,029 participants (6559 vaccine, 3470 placebo) who received two doses.

    “10 029 participants who received two doses of CoronaVac (6559 [65·4%] participants) or placebo (3470 [34·6%] participants) formed the per protocol population.”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data

    During a median follow-up of 43 days, 32 cases of PCR-confirmed symptomatic COVID-19 were reported in the placebo group.

    “and 32 cases were reported in the placebo group”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    There were no fatalities or grade 4 adverse events.

    “with no fatalities or grade 4 adverse events”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    The study population consisted of relatively young (median age 45 years [37-51]) and healthy individuals with a low prevalence of chronic diseases, and the overall event rate was very low.

    “Second, one should bear in mind that the study population consisted of relatively young (median age 45 years [37–51]) and healthy individuals with a low prevalence of chronic diseases, and the overall event rate was very low.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    Other local adverse events, including erythema, paraesthesia, and swelling, were rare and did not differ significantly in incidence between groups.

    “Other local adverse events, including erythema, paraesthesia, and swelling, were rare and did not differ significantly in incidence between groups (figure 5B).”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    There were no fatal cases of COVID-19.

    “There were no fatal cases of COVID-19.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    Seropositivity decreased with increasing age in women (ptrend=0.0003) and men (ptrend=0.0084).

    “Seropositivity decreased with increasing age in women (ptrend=0·0003) and men (ptrend=0·0084).”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    Hospitalisation was recorded in none of the participants in the vaccine group and six in the placebo group (36.4 hospitalisations per 1000 person-years, 95% CI 13.5-77.5).

    “Hospitalisation was recorded in none of the participants in the vaccine group and six in the placebo group (36·4 hospitalisations [13·5–77·5] per 1000 person-years)”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    The first participant with a serious adverse event had a grade 3 systemic allergic reaction that occurred more than 24 h after the administration of the first dose of vaccine and resolved uneventfully in the following 24 h.

    “The first participant had a grade 3 systemic allergic reaction that occurred more than 24 h after the administration of the first dose of vaccine and resolved uneventfully in the following 24 h.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    No grade 4 adverse events or deaths occurred during the study period.

    “The vaccine showed a satisfactory safety profile, with no grade 4 adverse events or deaths during the study period.”
    • Also stated in: § Discussion · plain
      “No grade 4 adverse events were observed and there was only one adverse event (an allergic reaction) that required hospitalisation.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    The most common solicited local reaction was inoculation site pain, which occurred significantly more frequently in the vaccine group (157 [2.4%] participants) than in the placebo group (40 [1.1%], p<0.0001).

    “The most common solicited local reaction was inoculation site pain, which occurred significantly more frequently in the vaccine group (157 [2·4%] participants) than in the placebo group (40 [1·1%], p<0·0001).”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    The other participant with a serious adverse event presented with seizure 43 days after the second dose of the vaccine; after an extensive work-up, this patient was diagnosed with an infiltrative glial neoplasm and, in the final assessment, this adverse event was judged to be unrelated to the vaccine.

    “The other participant presented with seizure 43 days after the second dose of the vaccine; however, after an extensive work-up, this patient was diagnosed with an infiltrative glial neoplasm and, in the final assessment, this adverse event was judged to be unrelated to the vaccine.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    Of the 41 cases, nine were in the vaccine group (n=6559; 31.7 cases per 1000 person-years, 95% CI 14.6-59.3) and 32 in the placebo group (n=3470; 192.3 cases per 1000 person-years, 95% CI 135.7-261.1).

    “Of these cases, nine were reported in the vaccine group (n=6559; 31·7 cases [14·6–59·3] per 1000 person-years) and 32 in the placebo group (n=3470; 192·3 cases [135·7–261·1] per 1000 person-years)”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim.

    Study design and conductnone given

    Participants and practitioners were masked to group allocation.

    “Participants and practitioners were masked to the group allocation.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisenone given

    CoronaVac provided a good humoral response against SARS-CoV-2 in phase 1/2 trials.

    “and provided a good humoral response against SARS-CoV-2.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Study design and conductreasoning

    The placebo and study vaccine looked exactly the same and were administered by staff masked to group allocation.

    “As the placebo and study vaccine looked exactly the same, they were administered by staff masked to group allocation.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductown data

    The study protocol was approved by the clinical research ethics board of Hacettepe University.

    “The study protocol was approved by the clinical research ethics board of Hacettepe University (approval number 2020/10-26, July 16, 2020).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductnone given

    Safety analyses were done in the intention-to-treat population.

    “Safety analyses were done in the intention-to-treat population.”
    • Also stated in: § Statistical analysis · plain
      “Safety analyses were done in the intention-to-treat population.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductnone given

    The study was registered with ClinicalTrials.gov (NCT04582344).

    “This study is registered with ClinicalTrials.gov (NCT04582344)”
    • Also stated in: § Statistical analysis · plain
      “This study is registered with ClinicalTrials.gov (NCT04582344).”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Interpretationown data

    CoronaVac has high efficacy against PCR-confirmed symptomatic COVID-19 with a good safety and tolerability profile.

    “CoronaVac has high efficacy against PCR-confirmed symptomatic COVID-19 with a good safety and tolerability profile.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Study design and conductown data

    The trial was double-blind, randomised, placebo-controlled, phase 3.

    “This was a double-blind, randomised, placebo-controlled phase 3 trial.”
    • Also stated in: § Study design and participants · plain
      “We did a double-blind, randomised, placebo-controlled, case-driven phase 3 clinical trial”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Study design and conductown data

    Randomisation into vaccine and placebo groups was done at a 1:1 ratio in K1 and a 2:1 ratio in K2 using an interactive web response system.

    “Randomisation into vaccine and placebo groups was done on day 0, at a 1:1 ratio in K1 and a 2:1 ratio in K2, using an interactive web response system (Omega-CRO, Ankara, Turkey).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Study design and conductnone given

    The independent data and safety monitoring board monitored the quality of evidence, adverse events, revisions, individual privacy, and data reliability.

    “The independent data and safety monitoring board monitored the quality of evidence, adverse events, revisions in line with the current literature, individual privacy, and data reliability from the planning stage to the end of the study.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim.

    Study design and conductown data

    The study was powered to detect a minimum clinically significant difference of 1% in incidence rates (1% vaccine vs 2% placebo) with 95% CIs.

    “Total sample sizes were calculated as 7545 for the vaccine group and 3773 for the placebo group in order to be able to detect a minimum clinically significant difference of 1% (with estimated incidence rates of 1% for the vaccine group and 2% for the placebo group) in a two-sided hypothesis testing design with 95% CIs.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductnone given

    Signed informed consent was obtained from participants before screening.

    “Signed informed consent was obtained from participants before screening.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Premisecitation

    The potential advantages of inactivated vaccines are non-replicability in the host, non-transmissibility, and induction of a broad range of humoral and cellular responses against different epitopes.

    “The potential advantages of inactivated vaccines are non-replicability in the host, non-transmissibility, and the induction of a broad range of humoral and cellular responses against different epitopes.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [7] Krammer, 2020, SARS-CoV-2 vaccines in development, Nature source

  • Probably not a substantial claim.

    Study design and conductnone given

    Clinical outcomes were assessed in a blinded manner.

    “Clinical outcomes were assessed in a blinded manner.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Interpretationown data

    CoronaVac fulfils the critical or minimal requirement of vaccines for pandemic use, hitting above the minimum efficacy of 50% specified by WHO.

    “The results of this interim analysis have shown that CoronaVac fulfils the critical or minimal requirement of vaccines for the indication of pandemic use, hitting above the minimum efficacy of 50% as specified by the WHO target product profile as an option for mass vaccination.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductreasoning

    We could not exclude the possibility that some samples with antibody levels below a sample-to-cutoff ratio of 1 might have very low concentrations of established antibodies.

    “However, we could not exclude the possibility that some samples with antibody levels below a sample-to-cutoff ratio of 1 might have very low concentrations of established antibodies.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    Palacios and colleagues reported an overall efficacy of CoronaVac against symptomatic COVID-19 of 50.7% (95% CI 36.0-62.0) 14 days or more after the second dose.

    “Palacios and colleagues22 reported an overall efficacy of CoronaVac against symptomatic COVID-19 of 50·7% (95% CI 36·0–62·0) 14 days or more after the second dose”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [22] Palacios, 2021, Efficacy and safety of a COVID-19 inactivated vaccine in healthcare professionals in Brazil: the PROFISCOV Study, SSRN source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Study design and conductreasoning

    Although one of the prespecified outcomes was seroconversion, we have avoided using this term in our reporting of the results because the immunoassay we used was a semiquantitative assay.

    “Although one of the prespecified outcomes was seroconversion, we have avoided using this term in our reporting of the results because the immunoassay we used was a semiquantitative assay.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Study design and conductown data

    The median follow-up period after randomisation to the date of unmasking was 43 days (IQR 36-48), which is a very short duration of follow-up.

    “First, the median follow-up period after randomisation to the date of unmasking was 43 days (IQR 36–48), which is a very short duration of follow-up.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductnone given

    All adverse events were assessed by study investigators for severity and causality.

    “All adverse events were assessed by study investigators for severity and causality.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Study design and conductreasoning

    The targeted sample size could not be reached because CoronaVac was granted emergency use authorisation by the Turkish Ministry of Health while the study recruitment was ongoing, and an immediate vaccination programme was initiated for health-care workers and later for the general public in Turkey.

    “The targeted sample size could not be reached because CoronaVac was granted emergency use authorisation by the Turkish Ministry of Health while the study recruitment was ongoing, and an immediate vaccination programme was initiated for health-care workers and later for the general public in Turkey.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductnone given

    All PCR and serum antibody tests were done at two central laboratories.

    “All PCR and serum antibody tests were done at two central laboratories.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Interpretationown data

    The number of patients hospitalised with COVID-19 was quite low and the study population consisted of individuals at relatively low risk of severe or critical COVID-19, restricting our ability to make generalised conclusions about severe disease.

    “In particular, the number of patients hospitalised with COVID-19 was quite low and the study population consisted of individuals at relatively low risk of severe or critical COVID-19, restricting our ability to make generalised conclusions about severe disease.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductnone given

    Active symptom surveillance was pursued to detect COVID-19 cases.

    “Additionally, active symptom surveillance was pursued to detect COVID-19 cases.”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Interpretationown data

    The generalisability of the findings of this interim analysis is limited by the young and healthy study population and the low event rate.

    “Therefore, the generalisability of the findings of this interim analysis needs to be evaluated cautiously.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    Production and scale-up of inactivated vaccines are relatively easy in the context of good yield production systems and availability of biosafety level 3 facilities.

    “Their production and scale-up are relatively easy in the context of good yield production systems and the availability of biosafety level 3 facilities.7”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [7] Krammer, 2020, SARS-CoV-2 vaccines in development, Nature source

  • It may state two separate claims as one.

    Study design and conductreasoning

    The strengths of this study include the low dropout rate, reflecting the good tolerability of the vaccine.

    “The strengths of this study include the low dropout rate, reflecting the good tolerability of the vaccine.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Interpretationreasoning

    All of the participants were seronegative at the time of screening; therefore, the seropositivity 14 days after the second dose of vaccine would indicate seroconversion.

    “In fact, all of the participants were seronegative at the time of screening; therefore, the seropositivity 14 days after the second dose of vaccine would indicate seroconversion.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Study design and conductnone given

    Efficacy in subgroups was not a secondary outcome and the trial was not designed or powered to analyse the efficacy of the vaccine with regard to demographic variables and risk factors.

    “Efficacy in subgroups was not a secondary outcome and the trial was not designed or powered to analyse the efficacy of the vaccine with regard to demographic variables and risk factors.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Interpretationown data

    The tolerability of CoronaVac in this study was excellent and the incidence of adverse events, most of which were solicited systemic events, was low.

    “The tolerability of CoronaVac in this study was excellent and the incidence of adverse events, most of which were solicited systemic events, was low.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Study design and conductnone given

    The current report neither involves data on the sequential serum neutralising antibody titres nor the magnitude of T-cell responses or the duration of protectivity.

    “The current report neither involves data on the sequential serum neutralising antibody titres nor the magnitude of T-cell responses or the duration of protectivity.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Interpretationown data

    In summary, our results show that CoronaVac has good efficacy against symptomatic SARS-CoV-2 infection and severe COVID-19 (ie, that requiring hospitalisation), along with a very good safety profile in a population aged 18-59 years.

    “In summary, our results show that CoronaVac has good efficacy against symptomatic SARS-CoV-2 infection and severe COVID-19 (ie, that requiring hospitalisation), along with a very good safety profile in a population aged 18–59 years.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Study design and conductnone given

    The study used a 14-day interval immunisation scheme, whereas the community immunisation was with a 28-day interval.

    “Third, the study used a 14-day interval immunisation scheme, whereas the community immunisation was with a 28-day interval.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Interpretationnone given

    The participants were from different risk groups and occupations, rendering the results of the study more generalisable to the real-world context.

    “Additionally, the participants were from different risk groups and occupations, rendering the results of the study more generalisable to the real-world context.”
    Quote in the paperSubstantial claim
54 of 54

  • The paper relies on this without support.

    A single dose of an inactivated vaccine is not expected to be as efficacious as two doses.

    “Because the study product is an inactivated vaccine, a single dose was not expected to be as efficacious as two doses, and the primary efficacy analysis was therefore done in the per protocol population”

  • The paper relies on this without support.

    A SN50 titre of at least 1/15 is a protective level of neutralising antibodies.

    “Virus neutralisation assays in selected samples (n=387) from seropositive participants in the vaccine group showed SN50s of at least 1/15 in 356 (92·0%) of the tested samples (figure 4 ).”
    “92·0% of those who were seropositive also produced protective levels of neutralising antibodies at least 14 days after the second dose of vaccine.”
2 of 2

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Person-year calculation is described in opposite directions

    Minor

    The methods first say total person-years were divided by COVID-19 cases, but the statistical analysis defines the rate as cases divided by person-years. These are reciprocal calculations.

  • Discussion denies an early effect that the results report

    Minor

    The results report statistically significant efficacy for cases occurring 14-27 days after the first dose, whereas the discussion says the study could not show an early protective effect after the first dose.

2 of 2

Citations

Cites

Flagged first, then by citations

Cited by

Sorted by citations

Related

Metadata

Authors
Tanriover, M. D., Doğanay, H. L., Akova, M., Güner, H. R., Azap, A., Akhan, S., Köse, Ş., Erdinç, F. Ş., Akalın, E. H., Tabak, Ö. F., Pullukçu, H., Batum, Ö., Şimşek Yavuz, S., Turhan, Ö., Yıldırmak, M. T., Köksal, İ., Taşova, Y., Korten, V., Yılmaz, G., Çelen, M. K., Altın, S., Çelik, İ., Bayındır, Y., Karaoğlan, İ., Yılmaz, A., Özkul, A., Gür, H., Unal, S., Kayaaslan, B., Hasanoğlu, İ., Dalkıran, A., Aydos, Ö., Çınar, G., Akdemir-Kalkan, İ., İnkaya, A. Ç., Aydin, M., Çakir, H., Yıldız, J., Kocabıyık, Ö., Arslan, S., Nallı, B., Demir, Ö., Singil, S., Ataman-Hatipoğlu, Ç., Tuncer-Ertem, G., Kınıklı, S., Önal, U., Mete, B., Dalgan, G., Taşbakan, M., Yamazhan, T., Kömürcüoğlu, B., Yalnız, E., Benli, A., Keskin-Sarıtaş, Ç., Ertosun, M. G., Özkan, Ö., Emre, S., Arıca, S., Kuşçu, F., Candevir, A., Ertürk-Şengel, B., Ayvaz, F., Aksoy, F., Mermutluoğlu, Ç., Demir, Y., Günlüoğlu, G., Tural-Önür, S., Kılıç-Toker, A., Eren, E., Otlu, B., Mete, A. Ö., Koçak, K., Ateş, H., Koca-Kalkan, İ., & Aksu, K.
Affiliations
  • Ümraniye Eğitim ve Araştırma Hastanesi (TR)
  • Hacettepe University (TR)
  • Ankara University (TR)
  • Kocaeli Üniversitesi (TR)
  • Izmir University (TR)
  • Ministry of Health (TR)
  • Istanbul University-Cerrahpaşa (TR)
  • Ege University (TR)
  • Sağlık Bilimleri Üniversitesi (TR)
  • Akdeniz University (TR)
  • Acıbadem University (TR)
  • Cukurova University (TR)
  • Marmara University (TR)
  • Dicle University (TR)
  • Inonu University (TR)
  • Gaziantep University (TR)
Corresponding author
Akova, Murat
ORCID
Venue
The Lancet
Publisher
Elsevier BV
Published
2021-07
Volume
398
Issue
10296
Pages
213-222
ISSN
  • 0099-5355 (ISSN-L)
  • 0140-6736
DOI
10.1016/s0140-6736(21)01429-x
PMC
PMC8266301
OpenAlex
W3178010802
Cited by
898
References
31
Citations by year
2026: 17 · 2025: 47 · 2024: 113 · 2023: 221 · 2022: 390 · 2021: 110
FWCI
66.15
Type
journal article
Language
en
Update notices
erratum (2022-01-29)
Open access
Licence
Locations
  • The Lancet (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
  • Bursa Uludag University - AVESIS (submittedVersion, cc-by-nc-nd)
  • Acibadem University Open Access Repository (submittedVersion)
  • Bursa Uludag University - AVESIS (submittedVersion)
  • Dspace Repository (Marmara Üniversitesi) (submittedVersion, other-oa)
Topics
  • Health Sciences › Medicine › Infectious Diseases › SARS-CoV-2 and COVID-19 Research
  • Health Sciences › Medicine › Infectious Diseases › COVID-19 Clinical Research Studies
  • Physical Sciences › Mathematics › Modeling and Simulation › COVID-19 epidemiological studies
Keywords
CoronaVac, COVID-19 vaccine efficacy, vaccine safety, healthcare workers, aluminum hydroxide adjuvant, humoral immune response, SARS-CoV-2, Turkey, interim results
MeSH terms
COVID-19, SARS-CoV-2, COVID-19 Vaccines, Antibodies, Viral, Double-Blind Method, Health Personnel, Humans, Male, Middle Aged, Turkey, Vaccination, Virion, Vaccines, Inactivated, Antibodies, Neutralizing

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

A language model drew the claims from the paper on 2026-10-28, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).

A second model labelled each claim on 2026-10-28 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).

Cited sources are checked with a language model’s help (gpt-6-sol).

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

Are you an author, or do you see a problem with this page? Request a review