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

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

47 Own result · 25 Own method · 13 Own interpretation · 6 Partly supported · 3 No full text of the sources · 2 Supported · 2 Not checked yet · 2 No basis given · accuracy not yet measured

Show all 46 claims

  • Probably not a substantial claim. 25
  • It may state two separate claims as one. 35
  • The quote only partly states this claim. 3
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.

2 of 2

Citations

Cites

Show all 31 references

Cited by

Sorted by citations

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
Venue
The Lancet
Publisher
Elsevier BV
Published
2021-07
Volume
398
Issue
10296
Pages
213-222
ISSN
  • 0099-5355 (ISSN-L)
  • 0140-6736
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
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