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A study was carried to explore the efficacy and safety of the ChAdOx1 nCoV-19 vaccine in a pooled interim assessment of 4 ongoing clinical trials.
The ChAdOx1 nCoV-19 (AZD1222) vaccine is
effective against symptomatic COVID-19 and has an acceptable safety profile.
A study was carried to explore
the efficacy and safety of the ChAdOx1 nCoV-19 vaccine in a pooled interim
assessment of 4 ongoing clinical trials.
The study incorporated data from four ongoing blinded, randomized, controlled trials: (i) COV001 (phase ½, United Kingdom), (ii) COV002 (phase II/III; United Kingdom), (iii) COV003 (phase III; Brazil), and (iv) COV005 (phase I/II; South Africa). Individuals (aged 18 years and older) were randomized to either the AZD1222 vaccine group or the control (meningococcal group A, C, W, and Y conjugate vaccine or saline) group. Subjects in the AZD1222 group were given two doses containing 5×10¹⁰ viral particles (standard dose; SD/SD); a subset in the United Kingdom trial that was given a half dose as their first dose (low dose) and a standard dose as their second dose (LD/SD).
The primary endpoint was symptomatic COVID-19 in
seronegative individuals with a nucleic acid amplification test-positive swab
more than 14 days after the second dosage of vaccine. Subjects were examined
based on therapy administered, with data cutoff on 4 November 2020. The
efficacy of AZD1222 was estimated as 1−relative
risk derived from a robust Poisson regression model adjusted for age. Overall,
23,848 subjects were recruited and 11,636 subjects were incorporated in the
interim primary efficacy analysis.
The overall vaccine efficacy, efficacy in subjects who were given two standard doses, and in subjects who were given a low dose followed by a standard dose is shown in the following table:
From
21 days following the initial dose, there were ten subjects hospitalized due to
coronavirus, all in the control group; two patients were found to suffer from
severe coronavirus disease, including one mortality. There were 74341
person-months of safety follow-up (median 3·4 months): 175 noxious effects
occurred in 168 subjects, 91 in the control group, and 84 events in the AZD1222 arm. Three events were classified as possibly linked to a
vaccine: one in the ChAdOx1 nCoV-19 arm, one in the control arm, and one in a
subject who remains masked to the cohort distribution.
ChAdOx1 nCoV-19 has a good
safety profile and is effective against symptomatic COVID-19, with no
hospitalizations or severe cases noted in the ChAdOx1 nCoV-19 recipients.
The Lancet
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
Merryn Voysey et al.
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