Safety and efficacy of single-dose Ad26.COV2.S vaccine against COVID-19

Author(s): Sadoff J, Gray G, Vandebosch A, et al.

Safety and efficacy of single-dose Ad26.COV2.S vaccine against COVID-19 - article image

NEJM Published online 21 April, 2021 |

Digest author: Stylianos Loukides, ERS E-Learning Director / 2 May, 2021

At this point, the pandemic is far from being over. Vaccines are representing significant interventions for controlling the pandemic. They could protect from the infection and they eliminate the spread of the disease.  The long-awaited results of the Ad26.COV2.S (Johnson & Johnson) vaccine against COVID-19 infection were recently published in The New England Journal of Medicine. The Ad26.COV2.S vaccine is a recombinant adenovirus vector vaccine that contains the entire SARS-CoV-2 virus Spike protein gene. In an international, phase 3, randomized, placebo-controlled study, patients were enrolled to receive either a single dose (5×1010 viral particles) of the vaccine or a placebo. The primary endpoints of the study were the efficacy of the vaccine against moderate and severe COVID-19 infection at least 14 and 28 days after vaccination in a population tested negative for SARS-CoV-2, and its control vaccine safety.

The study population included 19630 participants who received the vaccine and 19691 participants who received placebo. The study was conducted in countries with high prevalence of virus infection [Argentina, Brazil, Chile, Colombia, Mexico, Peru, South Africa, and the United States]. The median follow-up was 58 days (range, 1 to 124), and 55% of participants had at least 8 weeks of follow-up. 33% of the participants were ≥60 years old, while 40% had a co-existing condition.

The Ad26.COV2.S vaccine appeared to protect against moderate to severe COVID-19 disease after 14 days (116 cases in vaccinated and 348 in the placebo group,  efficacy 66.9%), and after 28 days (66 vs. 193 cases, efficiency 66.1%). The efficacy of the vaccine was greater for the very severe form of the disease at 14 days (76.7%) and 28 days (85.4%). Although 86 out of 91 cases in South Africa had strain 20H / 501Y.V2 (B.1.351 strain in South Africa) the efficacy of the vaccine was 52% and 64% at 14 and 28 days, respectively, against its moderate and severe form disease, while for the very severe form the respective percentages were 73.1% and 81.7%. The efficacy of the vaccine in the different subgroups appeared to be the same regardless of age (over or under 60 years) and co-morbidities. Also, some preliminary data show protection of at least 66% against asymptomatic disease, which helps to limit the spread of the virus. No adverse reactions were observed between the vaccine group and the placebo group, with 3 deaths reported in the vaccine group (none due to COVID-19) and 16 deaths in the placebo group (5 due to COVID-19).

The conclusion is that a single dose of the Johnson & Johnson vaccine protects against severe infection and death from COVID-19 infection, without mentioning significant safety concerns and possibly preventing asymptomatic disease, thus helping to reduce in the community. In addition, the effectiveness of the vaccine against the mutated strain of South Africa is maintained [52.0% against moderate to severe–critical disease and 73.1% against severe–critical disease with onset ≥14 days after administration; 64.0% against moderate to severe–critical disease and 81.7% against severe–critical disease with onset at ≥28 days after administration].

Another vaccine for the battle? Yes. A vaccine designed for a single dose which is the main difference compared to others. Some important issues raised in the current trial. The effectiveness against mutations like that of South Africa, the lower percentage of efficacy compared to m RNA ones and finally the efficacy against asymptomatic disease which is still unpowered since it failed to reach a high number of participants and the reported results are considered as preliminary.

General respiratory patient care
Public health
Respiratory digests
Respiratory infections