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

Abstract

Background: Results of a randomised trial showed the safety and efficacy of Gam-COVID-Vac against COVID-19. However, compared to other vaccines used across the globe, the real-world data on the effectiveness of Gam-COVID-Vac, especially against the disease caused by Delta variant of concern, was not available. We aimed to assess the effectiveness of vaccination mainly conducted with Gam-COVID-Vac in St. Petersburg, Russia. Methods: We designed a case-control study to assess the vaccine effectiveness (VE) against lung injury and referral to hospital. Self-reported vaccination status was collected for individuals with confirmed SARS-CoV-2 infection who were referred for initial low-dose computed tomography triage in two outpatient centres in July 3 -- August 9, 2021 in St. Petersburg, Russia. We used logistic regression models to estimate the adjusted (for age, and triage centre) VE for complete (>14 days after the second dose) and partial vaccination (>14 days after the first dose). We estimated the VE against referral for hospital admission, COVID-19-related lung injury assessed with LDCT, and decline in oxygen saturation. Results: In the final analysis, 13,894 patients were included, 1,291 (9.3%) of patients met our criteria for complete vaccination status, and 495 (3.6%) were referred to hospital. In the primary analysis, the adjusted VE against referral to hospital was 81% (95% CI: 68-88) for complete vaccination. The effect of the partial vaccination was not statistically significant. The VE against referral to hospital was more pronounced in women (84%, 95% CI: 66-92) compared to men (76%, 95% CI: 51-88). Vaccine protective effect increased with increasing lung injury categories, from 54% (95% CI: 48-60) against any sign of lung injury to 76% (95% CI: 59-86) against more than 50% lung involvement. A sharp increase was observed in the probability of hospital admission with age for non-vaccinated patients in relation to an almost flat relationship for the completely vaccinated group. Conclusions: COVID-19 vaccination was effective against referral to hospital in patients with symptomatic SARS-CoV-2 infection in St. Petersburg, Russia. This protection is probably mediated through VE against lung injury associated with COVID-19.

COVID-19 Vaccines: An Overview of Different Platforms

“…Subunit vaccines are potentially most susceptible to virus mutations, since they contain individual components of the virus or fragments of its proteins. For example, the effectiveness of the Novavax vaccine, which included the RBD domain, was two times lower in case of the Beta variant compared to the original SARS-CoV-2, being 50% [84].…”

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

“…Our cases were symptomatic patients with confirmed SARS-CoV-2 (using polymerase chain reaction (PCR) test) referred to low-dose computed tomography (LDCT) triage. Our previous report describes in detail the source and information we collected for the cases [7]. In brief, we collected individual-level data from two outpatient triage centres of the Medical Institute named after Berezin Sergey (MIBS), a private medical facility contracted by the city government to provide triage service for nearly half of the city districts.…”

“…Mounting evidence suggests that vaccines remain effective against new variants of SARS-CoV-2, the virus that started the COVID-19 pandemic. Studies of mRNA and vector-based vaccines used in different countries report acceptable levels of effectiveness against SARS-CoV-2 infection caused by the new variants of concern (VOC) [1][2][3][4][5][6][7]. Waning immunity against new VOCs is another emerging concern as the follow-up time after the start of the vaccination programmes increases [8].…”

“…However, the Hungary study covers the period before the spread of the Delta VOC. The case-control study in St. Petersburg was the first available evidence of vaccine effectiveness (VE) against referral to hospital in patients with symptomatic SARS-CoV-2 infection in Russia during the spread of the Delta VOC [7]. However, that study had several limitations.…”

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“…We fitted the demographic distribution of cellular and humoral immune memory levels elicited by different vaccines to independent lognormal distribution (data of CoronaVac 52 , Sputnik V [53][54][55] , ChAdOx1 nCoV-19 14,56,57 , and BNT162b2 58,59 ; details in Table S5) and assumed these data to be same as the immunogenicity data in the trials for vaccine efficacy estimation. The immunogenicity data can then be interpreted as vaccine efficacy based on demographic information embedded in the lognormal distribution.…”