New preliminary phase 3 data show the two-dose vaccine may even hold benefit for single-dose use.
The Russian coronavirus 2019 (COVID-19) vaccine—originally developed, distributed and researched among citizens with a veil of ambiguity—is linked to 91.6% efficacy, according to new phase 3 findings.
In newly published data from developers of the heterologous recombinant adenovirus (rAd) vaccine Gam-COVID-Vac (Sputnik V), investigators led by Denis Y. Logunov, DSc, reported preliminary results showing significant vaccine efficacy and general tolerability among 16,000-plus participants administered the two-dose vaccine.
The Gam-COVID-Vac, originally approved for use in Russia by its own government in mid-August 2020, is a two-part recombinant human adenovirus type 26 and type 5 vaccine (rAd26; rAd5). Both vaccine vectors carry the gene for full-length SARS-CoV-2 glycoprotein S.
It was previously assessed as a frozen and lyophilized formulation, and observed to have improved immunity with a booster doses of differing adenovirus types.
Logunov and colleagues conducted a randomized, double-blind, placebo-controlled phase 3 study across 25 hospitals and polyclinics in Moscow.
Participants were adults aged 18 years and older, with negative SARS-COV-2 PCR, IgG and IgM tests, no observed infectious diseases in the 14 days prior to enrollment, and no vaccinations in the 30 days prior to enrollment.
Investigators assigned participants 3:1 to either 0.5 mL/dose vaccine or placebo, stratified by age groups. The vaccine was administered as a first dose of rAd26, then a second dose of rAd5 21 days afterward.
The team sought a primary outcome of proportion of participants with PCR-confirmed COVID-19 from day 21 after receiving first vaccine dose. Trial protocol violations resulted in participant assessment exclusion—primary outcome-assessed participants had received 2 vaccine doses or placebo, safety-assessed participants had received at least 1 dose at the time of database lock, and rare adverse event-assessed participants had received 2 doses and had all available, verified data from a case report.
A total of 21,977 adults were randomly assigned to either Gam-COVID-Vac (n = 16,501) or placebo (n = 5476) between September 7 – November 24, 2020. The final primary outcome analysis included 19,866 participants.
The trial included 2144 participants aged 60 years or older, with a maximum age of 87 in the vaccine group.
From 21 days following the second vaccine dose, 16 (0.1%) of 14,964 vaccinated participants were diagnosed with COVID-19, versus 62 (1.3%) of 4902 placebo participants. Vaccine efficacy was reported as 91.6% (95% CI, 85.6 – 95.2),
Common, grade 1 adverse events comprised 94% of all reported events. Just 45 (0.3%) and 23 (0.4%) of vaccine and placebo participants, respectively, reported serious adverse events. Investigators reported none being associated with vaccination, with supporting confirmation from an independent data monitoring committee.
In a preliminary assessment of severe COVID-19 cases, investigators observed 100% efficacy with Gam-COVID-Vac (95% CI, 94.4 – 100).
An analysis of the severity of COVID-19 course among the two arms showed that, in the first 2 weeks after the first vaccine dose, there was no significant difference in severity of COVID-19 course between vaccine and placebo. From 15-21 days after the first dose, however, efficacy was observed at 73.6% (P = .048), then from day 21 and beyond, efficacy was 100% (P <.0001).
As of January 23, 2 million-plus doses of Gam-COVID-Vac have been administered to the public, investigators wrote, having been previously released in Russia for use in public, at-risk populations including medical workers and teachers.
The vaccine has additionally been assessed in clinical trials across Belarus, United Arab Emriates, and India.
Pharmacovigilance and monitoring for vaccine safety have been undertaken by the Federal Service for Surveillance in Healthcare.
Logunov and colleagues are additionally conducting an assessment of single-dose vaccine regimen, approved by an independent committee last month.
Though there is a need to better interpret duration of vaccine protection and continued safety monitoring, investigators noted that the preliminary results show promise for high efficacy, immunogenicity, and good tolerability for adults.