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Phase 1–2a Trial of Ad26.COV2.S COVID-19 Vaccine - COV1001
Contribution To Literature:
The COV1001 trial showed that vaccination with the Ad26.COV2.S vaccine had an acceptable safety and reactogenicity profile and was immunogenic after a single vaccination with either the low or high dose.
Description:
The goal of the trial was to assess the safety of coronavirus disease 2019 (COVID-19) vaccination with the Ad26.COV2.S vaccine.
Study Design
Patients were randomized in a 2:2:1 fashion to either low-dose vaccine (n = 162), high-dose vaccine (n = 158), or placebo (n = 82).
- Total number of enrollees: 402 (cohort 1); 403 (cohort 3)
- Duration of follow-up: 71 days
- Mean patient age: 35.4 years (cohort 1); 69.8 years (cohort 3)
- Percentage female: 52% (cohort 1); 50% (cohort 3)
Participants in cohorts 1 and 3 received Ad26.COV2.S at a dose of either 5×1010 viral particles (low dose) or 1×1011 viral particles (high dose) per milliliter, administered intramuscularly in a single-dose or two-dose schedule 56 days apart. The trial design called for an evaluation of the boosting effect of Ad26.COV2.S at 6 months and 1 year after vaccination with respect to safety, reactogenicity, and immunogenicity in each cohort.
Inclusion criteria:
- Age 18-55 years: This was divided into cohort 1a (with a target enrollment of 375 participants) and cohort 1b (an exploratory cohort for in-depth analysis of immunogenicity, with a target enrollment of 25 participants)
- Age ≥65 years: This consisted of cohort 3, with a target enrollment of 375 participants
Other salient features/characteristics:
- White 91% (cohort 1); 99% (cohort 3)
- Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seropositive: 2% (cohort 1); 1% (cohort 3)
Principal Findings:
The primary outcome, solicited local adverse events for low-dose vs. high-dose vs. placebo, was 64% vs. 78% vs. 9% (cohort 1); 41% vs. 42% vs. 14% (cohort 3).
- Solicited systemic adverse events: 65% vs. 84% vs. 26% (cohort 1); 46% vs. 55% vs. 23% (cohort 3)
Secondary outcomes:
- Cohort 1a: Binding-antibody geometric mean concentration (GMC) by day 29: 478 in low-dose/placebo group, 586 in the low-dose/low-dose group, 625 in the high-dose/placebo group, and 788 in the high-dose/high-dose group, with an incidence of seroconversion of ≥99% in all the groups
- Cohort 3: By day 29, the GMC was 312 in the low-dose group and 350 in the high-dose group, with 96% seroconversion
Interpretation:
The interim results of this trial indicate that vaccination with the Ad26.COV2.S vaccine had an acceptable safety and reactogenicity profile and was immunogenic after a single vaccination with either the low or high dose. Systemic side effects were higher particularly with the high dose, mostly consisting of fatigue, headache, and myalgias; these generally resolved within 24 hours. After the second dose among participants between the ages of 18 and 55 years, the incidence of grade 3 solicited systemic adverse events was much lower than that after the first immunization in both the low-dose and high-dose groups, a finding that contrasts with observations with respect to messenger RNA–based vaccines, for which the second dose has been associated with increased reactogenicity.
Ad26.COV2.S is a recombinant, replication-incompetent adenovirus serotype 26 (Ad26) vector encoding a full-length and stabilized SARS-CoV-2 spike (S) protein.
References:
Sadoff J, Le Gars M, Shukarev G, et al. Interim Results of a Phase 1–2a Trial of Ad26.COV2.S Covid-19 Vaccine. N Engl J Med 2021;Jan 13:[Epub ahead of print].
Clinical Topics: COVID-19 Hub, Prevention
Keywords: Adenoviridae, Antibody Formation, COVID-19, Fatigue, Headache, Myalgia, Primary Prevention, severe acute respiratory syndrome coronavirus 2, Vaccination, Vaccines
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