Safety and efficacy of an rAd26 and rAd5 vector-based heterologous prime-boost COVID-19 vaccine: an interim analysis of a randomised controlled phase 3 trial in Russia

Author(s): Logunov DY, Dolzhikova IV, Shcheblyakov DV et al

General respiratory patient care
Public health
Respiratory digests
Respiratory infections
Safety and efficacy of an rAd26 and rAd5 vector-based heterologous prime-boost COVID-19 vaccine: an interim analysis of a randomised controlled phase 3 trial in Russia - article image

Lancet Published Online February 2, 2021 https://doi.org/10.1016/ S0140-6736(21)00234-8

Digest Author(s): Stylianos Loukides, e-Learning Director / 7 February, 2021

The first results of the phase III trial of the Russian vaccine COVID-19, ‘Sputnik V’, have been published in ‘The Lancet’. This was a randomized double-blind, placebo-controlled, phase 3 trial at 25 hospitals and polyclinics in Moscow, Russia.

Summarizing the mechanism of the vaccine we must state that It uses 2 viral vectors: first for the first dose adenovirus 26 (Ad26) and then adenovirus 5 (Ad5). The use of two different ‘vaccines’, with an interval of 21 days, aims to overcome possible pre-existing adenovirus immunity in the population. The main difference with the Oxford-AstraZeneca vaccine is that 2 vectors are used (to transfer the information of the production of the spike protein to the cells) to activate the immune system against the virus. Inclusion criteria were age 18 years or older, a negative PCR test for COVID-19 plus negative anti-SARS-CoV-2 IgM and IgG antibody. Furthermore, no history of COVID-19 infection and no contact with anyone with COVID-19 in the preceding 14 day. Observation visits were planned for day 28, day 42 and day 180.

The efficacy of the vaccine, based on the number of confirmed cases of COVID-19, 21 days after the first dose of the vaccine (ie the day they would receive the second dose), was recorded as 91.6% (with confidence intervals of 85.6 –95.2). The results of the clinical trial show strong protection – and more than 87% – in all age groups of participants regardless of gender. This interim report of Phase III data presented includes results for more than 20,000 participants, 75% of whom received the vaccine. More specifically:

• The efficacy of the vaccine was 91.8% (67.1 – 98.3) in participants over 60 years of age.

• The efficacy of the vaccine against moderate or severe COVID-19 infection was 100% (94.4-100).

• From day 15 to day 21 after the first dose, the efficacy was 73.6%, and after day 21, the efficacy was 100%.

The most common adverse events were flu-like illness resulted in 15·2% and local reaction in 5.4% in the vaccine arm. There were three episodes of adverse events of grade 3 or worse, considered not associated with vaccination. All these adverse events were resolved.

Comment:

High efficacy and safety data are due to a single dose of the vaccine. The information about the production of the spike protein is carried by the viral vector Ad26. The (single-dose) Jansen / Johnson & Johnson vaccine also uses the Ad26 adenovirus and targets the spike protein. This high efficacy and reduction in disease severity after a single dose of the vaccine, however, is particularly encouraging for current dose-saving strategies.