COVID-19 vaccines effectiveness against symptomatic SARS-CoV-2 during Delta variant surge: a population-based case-control study in St. Petersburg, Russia

Abstract

Background: Studies of mRNA and vector-based vaccines used in different countries report acceptable levels of effectiveness against SARS-CoV-2 infection caused by the Delta variants of SARS-CoV-2. No studies estimated vaccine effectiveness (VE) of Gam-COVID-Vac and other vaccines used in Russia against symptomatic infection with Delta variant. In this population-based case-control study, we aimed to estimate the effectiveness of the Russian COVID-19 vaccines against symptomatic SARS-CoV-2 during the recent outbreak caused by the Delta VOC in October 2021 in St. Petersburg, Russia. Methods: In a population-based case-control study with density sampling of controls, we acquired information on cases and controls from two independent studies conducted in St. Petersburg. Cases were symptomatic patients with confirmed SARS-CoV-2 (using polymerase chain reaction (PCR) test) referred to low-dose computed tomography (LDCT) triage in two outpatient centres between October 6 and 14, 2021 during the Delta variant outbreak. We recruited the controls during the representative survey of the seroprevalence study conducted during the same period in St. Petersburg using random digit dialling. In the primary analysis, we used logistic regression models to estimate the adjusted (age, gender, and history of confirmed COVID-19) VE against symptomatic SARS-CoV-2 resulted in a referral to triage centre for three vaccines used in Russia: Gam-COVID-Vac, EpiVacCorona, and CoviVac. Findings: We included 1,198 cases and 2,747 controls recruited between the 6th and 14th of October in the final analysis. VE was 58% (95% CI: 50; 64) for Gam-COVID-Vac (Sputnik V), 50% (95% CI: 30; 64) for 1-dose Gam-COVID-Vac (Sputnik V) or Sputnik Light, -40% (95% CI: -191; 33) for EpiVacCorona and 38% (95% CI: 0; 62) for CoviVac. Without adjustment for the history of confirmed COVID-19 VE for all vaccines was lower, except for one-dose Gam-COVID-Vac (Sputnik Light). The adjusted VE was slightly lower in women - 52% (95% CI: 41; 62) than men - 66% (95% CI: 55; 74). It was also higher in younger age. However, in the analysis restricted to participants without a history of confirmed COVID-19, the differences in VE by age group were smaller. Interpretation: In contrast to other Russian vaccines, Gam-COVID-Vac is effective against symptomatic SARS-CoV-2 infection caused by Delta VOC. Effectiveness is likely higher than the estimated 58% due to bias arising from high prevalence of the past COVID-19 in St. Petersburg. Funding: Population-based survey in St. Petersburg was funded by Polymetal International, plc.

Retrospective Cohort Study of the Effectiveness of the Sputnik V and EpiVacCorona Vaccines against the SARS-CoV-2 Delta Variant in Moscow (June–July 2021)

“…We find that the estimated VE of the Sputnik V vaccine to prevent deaths and severe forms of disease caused by the Delta variant of SARS-CoV-2 is comparable to the estimated VE of this vaccine against COVID-19 caused by other viral variants that have previously appeared in circulation. Our observations are consistent with other studies that have evaluated the VE of Sputnik V in clinical trials [ 6 ] or case-control studies [ 41 ]. However, due to several factors, and primarily due to the limitations of the database with which we worked, it was impossible to directly compare the estimated VE values in our work with VE estimates from published papers.…”

“…To date, the developers of EpiVacCorona have not published the results of their phase III study. The results of this analysis, along with an earlier analysis [ 41 ], indicate a lack of protective VE. Our study showed the negative efficacy of EpiVacCorona.…”

Vaccine Effectiveness against Referral to Hospital and Severe Lung Injury Associated with COVID-19: A Case-Control Study in St. Petersburg, Russia

“…However, in its response to an inquiry by a member of St. Petersburg Legislative Assemblу city Health Committee revealed that, by July 23, 2021, in St. Petersburg, among 1,227,496 individuals who received at least one vaccine dose, 1,178,266 or 96% received GamCOVIDVac, and the rest is distributed between the other two vaccines (EpiVacCorona -21,943 or 1.7% and KoviVac 27,287 or 2.2%) [19]. October 2021 survey showed that only about 10% of responders in St. Petersburg received a vaccine other than GamCOVIDVac [22]. It is safe to assume that our study approximates the effectiveness of GamCOVID Vac.…”

“…The majority of vaccinated residents in St. Petersburg received Gam-COVID-Vac. The proportion of the population that received other vaccines was 10% or less in St. Petersburg [19, 22].…”

Data and distrust hamper Russia’s vaccination programme

“…The true immunogenicity of EpiVacCorona appeared to be lower than declared (70% versus the 100% claimed in official statements). Moreover, as a preprint stated, “immunisation with this vaccine did not lead to emergence of neutralising antibodies in healthy volunteers.” Two further1011 preprints have since been issued (one by a group of epidemiologists from St Petersburg, the other by a scientist and a science journalist), both claiming negative efficacy for EpiVacCorona. This could also be because of the small size of the cohort studied, or because of the tendency in vaccinated people to be less cautious about spreading infection, preprint authors suggested.…”