The DOI matches its Crossref record; 24 of the 24 references it cites were found in a registry or an index; none of the 14 sources its claims cite is checked for support yet.
Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant
Open accessPublished version of a preprint
Abstract
BACKGROUND: Assessment of the safety and efficacy of vaccines against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in different populations is essential, as is investigation of the efficacy of the vaccines against emerging SARS-CoV-2 variants of concern, including the B.1.351 (501Y.V2) variant first identified in South Africa. METHODS: viral particles or placebo (0.9% sodium chloride solution) 21 to 35 days apart. Serum samples obtained from 25 participants after the second dose were tested by pseudovirus and live-virus neutralization assays against the original D614G virus and the B.1.351 variant. The primary end points were safety and efficacy of the vaccine against laboratory-confirmed symptomatic coronavirus 2019 illness (Covid-19) more than 14 days after the second dose. RESULTS: Between June 24 and November 9, 2020, we enrolled 2026 HIV-negative adults (median age, 30 years); 1010 and 1011 participants received at least one dose of placebo or vaccine, respectively. Both the pseudovirus and the live-virus neutralization assays showed greater resistance to the B.1.351 variant in serum samples obtained from vaccine recipients than in samples from placebo recipients. In the primary end-point analysis, mild-to-moderate Covid-19 developed in 23 of 717 placebo recipients (3.2%) and in 19 of 750 vaccine recipients (2.5%), for an efficacy of 21.9% (95% confidence interval [CI], -49.9 to 59.8). Among the 42 participants with Covid-19, 39 cases (95.1% of 41 with sequencing data) were caused by the B.1.351 variant; vaccine efficacy against this variant, analyzed as a secondary end point, was 10.4% (95% CI, -76.8 to 54.8). The incidence of serious adverse events was balanced between the vaccine and placebo groups. CONCLUSIONS: A two-dose regimen of the ChAdOx1 nCoV-19 vaccine did not show protection against mild-to-moderate Covid-19 due to the B.1.351 variant. (Funded by the Bill and Melinda Gates Foundation and others; ClinicalTrials.gov number, NCT04444674; Pan African Clinical Trials Registry number, PACTR202006922165132).
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Geometric mean titers dropped from 297 against the original virus to 85 against the RBD-only mutant and 74 against the B.1.351 variant.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Results > Immunogenicity
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“A total of 1467 seronegative participants (750 assigned to the vaccine and 717 to placebo) were eligible for the primary efficacy analysis; reasons for exclusion are listed in Figure 1.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Results > Participants
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesNone of the sources cited for this claim have been checked yet.
In the paper
“In a post hoc analysis of vaccine efficacy at more than 14 days after a single injection through October 31, 2020, as a proxy for infection by a non–B.1.351 variant (Fig. S1),15,27 the overall attack rate of mild-to-moderate Covid-19 at least 14 days after the first injection was 1.3% in placebo recipients and 0.3% in vaccine recipients; vaccine efficacy was 75.4% (95% CI, 8.7 to 95.5) (Table S8).”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Results > Vaccine Efficacy
What the sources say
- Not checked yetcites [15] Tegally H, Wilkinson E, Giovanetti M, et al. Emergence and rapid spread of a new severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) lineage with multiple spike mutations in South Africa. December 22, 2020 (https://www.medrxiv.org/content/10.1101/2020.12.21.20248640v1). preprint.
- Not checked yetcites [27] National Institute for Communicable Diseases. Dominance of the SARS-CoV-2 501Y.V2 lineage in Gauteng. January 28, 2021 (https://www.nicd.ac.za/wp-content/uploads/2021/01/Dominance-of-the-SARS-CoV-2-501Y.V2-lineage-in-Gauteng-South-Africa-1.pdf.) preprint.
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Both the pseudovirus and the live-virus neutralization assays showed greater resistance to the B.1.351 variant in serum samples obtained from vaccine recipients than in samples from placebo recipients.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Abstract > Results
Strength:plain· not yet calibratedCausal:correlational· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Live-virus assay showed lower neutralization overall, relative to pseudovirus assay (Figure 2C).”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Results > Immunogenicity
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The incidence of serious adverse events was balanced between the vaccine and placebo groups.”
- Also stated in: § Safety · plain
“The incidence of adverse events and serious adverse events was similar among vaccine and placebo recipients (Tables S3 and S4).”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Abstract > Results
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passes- Also stated in: § Safety · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Of 87 spike-specific antigens identified by the sequencing, 75 remained unaffected by the B.1.351 mutations.”
- Also stated in: § Discussion · plain
“In a post hoc analysis reported here, we found that in spike-specific T cells that expanded after vaccination with ChAdOx1 nCoV-19, the majority of antigens and epitopes remained intact in recognition of the B.1.351 variant.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Results > Immunogenicity
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Also stated in: § Discussion · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Overall vaccine efficacy for Covid-19 of any degree of severity more than 14 days after the first dose was 33.5% (95% CI, −13.4 to 61.7).”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Results > Vaccine Efficacy
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In a secondary-outcome analysis, efficacy against B.1.351 was not evident (vaccine efficacy, 10.4%; 95% CI, −76.8 to 54.8) (Table 2).”
- Also stated in: § Results · plain
“Among the 42 participants with Covid-19, 39 cases (92.9%) were caused by the B.1.351 variant; vaccine efficacy against this variant, analyzed as a secondary end point, was 10.4% (95% CI, −76.8 to 54.8).”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Results > Vaccine Efficacy
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Also stated in: § Results · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Among the 42 participants with Covid-19, 39 cases (92.9%) were caused by the B.1.351 variant; vaccine efficacy against this variant, analyzed as a secondary end point, was 10.4% (95% CI, −76.8 to 54.8).”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Abstract > Results
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes
- It may state two separate claims as one. 17
- Probably not a substantial claim. 10
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In the primary end-point analysis, mild-to-moderate Covid-19 developed in 23 of 717 placebo recipients (3.2%) and in 19 of 750 vaccine recipients (2.5%), for an efficacy of 21.9% (95% confidence interval [CI], −49.9 to 59.8).”
- Also stated in: § Vaccine Efficacy · plain
“The incidence of confirmed mild-to-moderate Covid-19 more than 14 days after the second dose among previously seronegative participants was 93.6 per 1000 person-years in the placebo group and 73.1 per 1000 person-years in the vaccine group; vaccine efficacy was 21.9% (95% CI, −49.9 to 59.8) (Table 2 and Figure 3).”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Abstract > Results
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
- Also stated in: § Vaccine Efficacy · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“All 42 cases of Covid-19 were graded as mild (15 vaccine recipients and 17 placebo recipients) or moderate (4 vaccine recipients and 6 placebo recipients); there were no cases of severe disease or hospitalization in either group.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Results > Vaccine Efficacy
Strength:plain· not yet calibratedn = 42Tests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Between June 24 and November 9, 2020, we enrolled 2026 HIV-negative adults (median age, 30 years); 1010 and 1011 participants received at least one dose of placebo or vaccine, respectively.”
- Also stated in: § Participants · plain
“We screened 3022 persons across seven sites and enrolled 2026 HIV-negative persons in the trial between June 24 and November 9, 2020.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Abstract > Results
Strength:plain· not yet calibratedn = 2,026Tests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
- Also stated in: § Participants · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Humoral response to the ChAdOx1 nCoV-19 vaccine induced strong neutralizing antibodies at 28 days after the first dose (geometric mean titer, 132; interquartile range, 20 to 404), which rose further after a second dose (geometric mean titer, 277; interquartile range, 124 to 526) (Figure 2A and Table S5).”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Results > Immunogenicity
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Seven of the 12 participants (58%) with neutralization activity against B.1.1 had undetectable neutralization activity against the B.1.351 variant, and the remaining 5 showed neutralization that was lower by a factor of 4.1 to 31.5 (Figure 2C).”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Results > Immunogenicity
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Among the six placebo recipients recently infected with SARS-CoV-2, all had detectable neutralization of the B.1.1 variant, whereas neutralization activity against the B.1.351 variant was undetectable in two cases, lower neutralization by a factor of 6.0 to 9.5 was noted in three cases, and no change was seen in one case (Figure 2C).”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Results > Immunogenicity
Strength:plain· not yet calibratedn = 3Tests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Forty-one of the 42 nasal swab samples (97.6%) were successfully sequenced and classified; 39 (95.1%) cases were caused by the B.1.351 variant and 2 (4.9%; both in the placebo group) by the B.1.1.1 and B.1.144 lineages (Fig. S8).”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Results > Vaccine Efficacy
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Similarly, among seropositive participants who had had a nonreactive nucleic acid amplification test before or at randomization, the incidence of mild-to-moderate Covid-19 more than 14 days after the second injection did not differ between placebo (81.9 per 1000 person-years) and vaccine (73.2 per 1000 person-years) recipients; vaccine efficacy was 10.6% (95% CI, −66.4 to 52.2) (Table S6).”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Results > Vaccine Efficacy
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Six of 13 vaccine recipients (46%) without evidence of previous SARS-CoV-2 infection showed no neutralization activity against an RBD triple-mutant pseudovirus (containing K417N, E484K, and N501Y variants), and 11 of the 13 (85%) had no neutralization activity against B.1.351 pseudovirus (Figure 2B).”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Results > Immunogenicity
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The only serious adverse event attributed to the ChAdOx1 nCoV-19 vaccine was a body temperature above 40°C after the first dose; the fever subsided within 24 hours, and no reactogenicity was observed after the second dose.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Results > Safety
Tests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Covid-19 cases were evaluated by at least two physicians who were independent of the trial and were unaware of trial-group assignments.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Methods > Efficacy Objectives
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“In this multisite, double-blind, randomized, placebo-controlled trial conducted in South Africa, we assessed the safety and efficacy of two standard doses of the ChAdOx1 nCoV-19 vaccine, administered 21 to 35 days apart, as compared with saline (0.9% sodium chloride) placebo.”
- Also stated in: § Methods · plain
“We conducted a multicenter, double-blind, randomized, controlled trial to assess the safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) in people not infected with the human immunodeficiency virus (HIV) in South Africa.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Methods > Trial Objectives, Participants, and Oversight
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- Also stated in: § Methods · plain
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Confidence intervals reported in this article have not been adjusted for multiple comparisons.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Methods > Statistical Analysis
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Participants 18 to less than 65 years of age were assigned in a 1:1 ratio to receive two doses of vaccine containing 5×1010 viral particles or placebo (0.9% sodium chloride solution) 21 to 35 days apart.”
- Also stated in: § Trial Procedures · plain
“Trial participants were randomly assigned to receive either a 0.33-to-0.5-ml dose (depending on the lot) of the ChAdOx1 nCoV-19 vaccine or placebo by intramuscular injection on the day of randomization and a second injection 21 to 35 days later.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Abstract > Methods
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim. It may state two separate claims as one.
- Also stated in: § Trial Procedures · plain
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“An independent data and safety monitoring committee reviewed efficacy and unblinded safety data.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Methods > Trial Objectives, Participants, and Oversight
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“The primary efficacy analysis was end-point–driven for the composite of mild, moderate, or severe Covid-19 and required 42 cases to detect a vaccine efficacy of at least 60% (with a lower bound of 0% for the 95% confidence interval), with 80% power.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Methods > Statistical Analysis
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Testing of neutralizing antibody activity against the original virus and the B.1.351 variant was undertaken before unblinding of trial-group assignments.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Methods > Neutralization Assays
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“Interim results from South Africa reported a vaccine efficacy of 57% against moderate-to-severe Covid-19 and 89% against severe Covid-19 mainly due to the B.1.351 variant.13”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Discussion
What the sources say
- Not checked yetcites [13] Johnson & Johnson. Johnson & Johnson COVID-19 vaccine authorized by U.S. FDA for emergency use — first single-shot vaccine in fight against global pandemic. February 27, 2021 (https://www.jnj.com/johnson-johnson-announces-single-shot-janssen-covid-19-vaccine-candidate-met-primary-endpoints-in-interim-analysis-of-its-phase-3-ensemble-trial).
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“The trial was monitored by an external clinical research organization, which ensured adherence to the protocol.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Methods > Trial Objectives, Participants, and Oversight
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Of note, the vaccine efficacy in preventing Covid-19 due to the B.1.351 variant was estimated in a secondary analysis; the trial was powered for the primary objective of a vaccine efficacy of at least 60% in preventing Covid-19 of any severity, irrespective of variants.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Discussion
Load-bearingStrength:hedged· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“Neutralizing activity of the two mRNA vaccines against the B.1.351 variant has also been observed to be lower, by a factor of 8.6 (mRNA-1273 vaccine [Moderna]) or 6.5 (BNT-162b2 vaccine [Pfizer]) on pseudovirus neutralization assay, than activity against the D614G virus, whereas no difference was evident against the N510Y.V1 (B.1.1.7)–like mutant.19,28,29”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Discussion
What the sources say
- Not checked yetcites [19] Wang P, Liu L, Iketani S, et al. Increased resistance of SARS-CoV-2 variants B.1.351 and B.1.1.7 to antibody neutralization. January 26, 2021 (https://www.biorxiv.org/content/10.1101/2021.01.25.428137v1). preprint. source
- Not checked yetcites [28] Muik A, Wallisch A-K, Sänger B, et al. Neutralization of SARS-CoV-2 lineage B.1.1.7 pseudovirus by BNT162b2 vaccine-elicited human sera. Science 2021 January 29 (Epub ahead of print). 33514629 PMC7971771 source
- Not checked yetcites [29] Liu Y, Liu J, Xia H, et al. Neutralizing activity of BNT162b2-elicited serum. N Engl J Med. DOI: 10.1056/NEJMc2102017. PMC7944950 33684280 source
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
In the paper
“The sensitivity of B.1.351 to neutralizing antibodies from convalescent donors infected with the prototype lineage virus, assessed with a spike-pseudovirus neutralization assay, indicated that 48% of serum samples were unable to neutralize B.1.351, with the rest showing a reduction in neutralization titers by a factor of 3 to 86.21”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Abstract > Conclusions
What the sources say
- Not checked yetcites [21] Wibmer CK, Ayres F, Hermanus T, et al. SARS-CoV-2 501Y.V2 escapes neutralization by South African COVID-19 donor plasma. Nat Med 2021 March 2 (Epub ahead of print). 33654292 source
Load-bearingStrength:hedged· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Injections were prepared and administered by site staff who were aware of participants’ trial-group assignments but were not involved in any other trial procedures. Trial participants and all other trial staff remain unaware of trial-group assignments.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Methods > Trial Procedures
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Vaccine efficacy against the B.1.351 variant was a prespecified secondary objective.”
§ Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant > Methods > Efficacy Objectives
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
In the citing paper
“recent reports suggest that these variants are partially resistant to neutralization by monoclonal antibodies against spike protein, by convalescent plasma and, notably, by sera from participants who have received severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines91,94,95.”
From Prospects for durable immune control of SARS-CoV-2 and prevention of reinfection (2021) · cites this paper as [95]
In the citing paper
“Alternatively, if the loss of antibody neutralization abrogates protection even when T cell recognition is maintained, this suggests a primary role for neutralizing antibodies95.”
From Prospects for durable immune control of SARS-CoV-2 and prevention of reinfection (2021) · cites this paper as [95]
In the citing paper
“Concerning neutralization of VOCs, recent studies have consistently reported lower neutralizing antibody titers against B.1.351 after vaccination but not against B.1.1.7 (39, 42, 48–59).”
From SARS-CoV-2 variants of concern partially escape humoral but not T cell responses in COVID-19 convalescent donors and vaccine recipients (2021) · cites this paper as [39]
In the citing paper
“Several studies have now shown that there is reduced vaccine efficacy against mild to moderate disease in countries where B1.351 was dominant (Zhou et al., 2021; Shinde et al., 2021; Madhi et al., 2021, Vaccines and Related Biological Products Advisory Committee, 2021), although protection against severe disease appears to be preserved.”
From Reduced neutralization of SARS-CoV-2 B.1.617 by vaccine and convalescent serum (2021) · cites this paper as Madhi et al., 2021
In the citing paper
“ChAdOx1-nCoV19 was evaluated in a phase 2 trial (N=2026) in South Africa, in a study population resembling ours with predominantly mild to moderate Covid-19, and reported vaccine efficacy of 22% (95% CI: −50 to 60) overall, and 10% (95% CI: −77 to 55) against the B.1.351 variant, with the latter comprising 95% of cases.25”
From Efficacy of NVX-CoV2373 Covid-19 Vaccine against the B.1.351 Variant (2021) · cites this paper as [25]
In the citing paper
“Of plasma samples from persons receiving the AZD1222 vaccine, 42% had 3-fold to 10-fold and 54% had >10-fold reduced Beta variant neutralizing activity 104,214,224 (fIg.5).”
From The biological and clinical significance of emerging SARS-CoV-2 variants (2021) · cites this paper as [224]
In the citing paper
“In a phase II trial in South Africa of AZD1222 in which 39 HIV-negative patients became infected with the Beta variant, the estimated vaccine efficacy was just 10% 224 .”
From The biological and clinical significance of emerging SARS-CoV-2 variants (2021) · cites this paper as [224]
In the citing paper
“Neutralizing antibodies are a likely correlate of protection against SARS-CoV-2 infection, as suggested by vaccine efficacy studies, preclinical studies in mice and non-human primates, and data from the early use of convalescent plasma in elderly patients 4,5,10,13,14,18,23 .”
From Age-related immune response heterogeneity to SARS-CoV-2 vaccine BNT162b2 (2021) · cites this paper as [10]
In the citing paper
“In addition, the emergence of new variants with increased transmissibility 8 and reduced sensitivity to vaccine-elicited antibodies 9 , and for which vaccines are less able to prevent infection 10 , has raised fears for vulnerable groups in whom the magnitude and quality of immune responses may be suboptimal.”
From Age-related immune response heterogeneity to SARS-CoV-2 vaccine BNT162b2 (2021) · cites this paper as [10]
In the citing paper
“Initial reports from clinical trials or from breakthrough community infections suggest that current vaccines might be less protective against symptomatic infection with some SARS-CoV-2 variants.5, 6”
From Neutralising antibody titres as predictors of protection against SARS-CoV-2 variants and the impact of boosting: a meta-analysis (2022) · cites this paper as [5]
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.
Vaccine and placebo recipient counts are reversed
MinorThe abstract assigns 1010 recipients to placebo and 1011 to vaccine, while the Results section assigns 1010 to vaccine and 1011 to placebo.
“1010 and 1011 participants received at least one dose of placebo or vaccine, respectively.”
“Overall, 1010 participants received the vaccine and 1011 received the placebo (Figure 1).”
Citations
Cites
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Metadata
- Authors
- Madhi, S. A., Baillie, V., Cutland, C. L., Voysey, M., Koen, A. L., Fairlie, L., Padayachee, S. D., Dheda, K., Barnabas, S. L., Bhorat, Q. E., Briner, C., Kwatra, G., Ahmed, K., Aley, P., Bhikha, S., Bhiman, J. N., Bhorat, A. E., du Plessis, J., Esmail, A., Groenewald, M., Horne, E., Hwa, S.-H., Jose, A., Lambe, T., Laubscher, M., Malahleha, M., Masenya, M., Masilela, M., McKenzie, S., Molapo, K., Moultrie, A., Oelofse, S., Patel, F., Pillay, S., Rhead, S., Rodel, H., Rossouw, L., Taoushanis, C., Tegally, H., Thombrayil, A., van Eck, S., Wibmer, C. K., Durham, N. M., Kelly, E. J., Villafana, T. L., Gilbert, S., Pollard, A. J., de Oliveira, T., Moore, P. L., Sigal, A., & Izu, A.
- Affiliations
- South African Medical Research Council (ZA)
- University of the Witwatersrand (ZA)
- University of Oxford (GB)
- Setshaba Research Centre (ZA)
- University of Cape Town (ZA)
- Stellenbosch University (ZA)
- Soweto CTC (ZA)
- National Health Laboratory Service (ZA)
- Africa Health Research Institute (ZA)
- Max Planck Institute for Infection Biology (DE)
- AstraZeneca (United Kingdom) (GB)
- From the South African Medical Research Council Vaccines and Infectious Diseases Analytics Research Unit (S.A.M., V.B., A.L.K., G.K., S.B., J.P., A.J., M.L., S.M., A.M., C.T., A.T., A.I.), African Leadership in Vaccinology Expertise (C.L.C.), Wits Reproductive Health and HIV Institute (L.F., E.H., M. Masenya, F.P., S.E.), the Antibody Immunity Research Unit, School of Pathology (J.N.B., C.K.W., P.L.M.), and the Perinatal HIV Research Unit (C.B.), Faculty of Health Sciences, and the Department of Science and Innovation/National Research Foundation South African Research Chair Initiative in Vaccine Preventable Diseases Unit (S.A.M., V.B., A.L.K., G.K., S.B., A.I.), University of the Witwatersrand, and the National Institute for Communicable Diseases (NICD) of the National Health Laboratory Service (NHLS) (J.N.B., C.K.W., P.L.M.), Johannesburg, Setshaba Research Centre, Tshwane (S.D.P., K.A., M. Malahleha, M. Masilela, K.M.), the Division of Pulmonology, Groote Schuur Hospital and the University of Cape Town ...
- Corresponding author
- Madhi, Shabir A.
- ORCID
- Madhi, Shabir A.
- Baillie, Vicky
- Cutland, Clare L.
- Voysey, Merryn
- Koen, Anthonet L.
- Fairlie, Lee
- Dheda, Keertan
- Barnabas, Shaun L.
- Bhorat, Qasim E.
- Briner, Carmen
- Kwatra, Gaurav
- Ahmed, Khatija
- Aley, Parvinder
- Bhiman, Jinal N.
- Bhorat, As’ad E.
- Esmail, Aliasgar
- Horne, Elizea
- Hwa, Shi-Hsia
- Lambe, Teresa
- Laubscher, Matt
- Malahleha, Mookho
- Masenya, Masebole
- Moultrie, Andrew
- Oelofse, Suzette
- Patel, Faeezah
- Pillay, Sureshnee
- Rhead, Sarah
- Rodel, Hylton
- Taoushanis, Carol
- Tegally, Houriiyah
- Wibmer, Constantinos K.
- Durham, Nicholas M.
- Kelly, Elizabeth J.
- Villafana, Tonya L.
- Gilbert, Sarah
- Pollard, Andrew J.
- Moore, Penny L.
- Sigal, Alex
- Izu, Alane
- Venue
- New England Journal of Medicine
- Publisher
- Massachusetts Medical Society
- Published
- 2021-05-20
- Volume
- 384
- Issue
- 20
- Pages
- 1885-1898
- ISSN
- 0028-4793 (ISSN-L)
- 1533-4406
- PMC
- PMC7993410
- OpenAlex
- W3139533040
- Cited by
- 1,257
- References
- 23
- Citations by year
- 2026: 9 · 2025: 33 · 2024: 64 · 2023: 135 · 2022: 413 · 2021: 600
- FWCI
- 96.76
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- Locations
- New England Journal of Medicine (publishedVersion, cc-by)
- medRxiv (acceptedVersion, cc-by-nc-nd)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- LSHTM Research Online (London School of Hygiene and Tropical Medicine) (acceptedVersion)
- Funders
- Bill and Melinda Gates Foundation (INV-017710)
- South African Medical Research Council (96167)
- U.K. Research and Innovation (MC_PC_19055)
- UK National Institute for Health Research
- Topics
- Health Sciences › Medicine › Infectious Diseases › SARS-CoV-2 and COVID-19 Research
- Health Sciences › Medicine › Infectious Diseases › COVID-19 Clinical Research Studies
- Social Sciences › Health › Vaccine Coverage and Hesitancy
- Keywords
- ChAdOx1 nCoV-19 vaccine, COVID-19 vaccine efficacy, B.1.351 variant, SARS-CoV-2 variants of concern, neutralizing antibodies, pseudovirus neutralization, symptomatic COVID-19, vaccine safety, adenovirus vector vaccine
- MeSH terms
- Immunogenicity, Vaccine, COVID-19, SARS-CoV-2, COVID-19 Vaccines, COVID-19 Serological Testing, ChAdOx1 nCoV-19, Adenoviridae, Adolescent, Adult, Double-Blind Method, Humans, Middle Aged, South Africa, T-Lymphocytes, Treatment Failure, Young Adult, Antibodies, Neutralizing, Vaccine Potency
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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.
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