Performance of vaccination with CoronaVac in a cohort of healthcare workers (HCW) - preliminary report

Abstract

Background: CoronaVac, a vaccine containing inactivated SARS-CoV-2, demonstrated efficacy of 50.39% 14 days or more after the 2nd dose. The objective of this study is to report the occurrence of symptomatic COVID-19 in a cohort of HCW vaccinated with CoronaVac and to estimate its effectiveness. Methods: CoronaVac was given to HCWs in Hospital das Clinicas on 18-21 January, 2021 (epi week 3) (22,402 HCWs), and on 14-16 February, 2021 (epi week 7) (21,652 HCWs). Weekly cases of symptomatic COVID-19 were evaluated. Using the period from 2020 epi week 24 through 2021 epi week 2 (before vaccination), a Poisson regression was fit to model the HCWs with COVID-19 of the hospital, and the officially reported cases in the city of Sao Paulo. The predicted numbers of cases among HCWs for 2021 epi weeks 3-12 were then compared to the observed numbers of cases (after vaccination). Effectiveness was estimated for weeks 9-12 (2 to 5 weeks after the 2nd dose). 142 samples after vaccination were evaluated for SARS-CoV-2 variants of concern. Results: Since the 1st dose there were 380 HCW diagnosed with COVID-19. On visual analysis, the number of cases of COVID-19 in the city increased sharply in 2021. The number of cases among the HCW did not follow. The estimated effectiveness 2 and 3 weeks after 2nd dose was 50.7% and 51.8%, respectively, and increased over the next 2 weeks. 67/142 samples (47%) were variants of concern, mostly P1 (57). Conclusion: Coronavac is effective in preventing COVID-19.

What Happens to the Immune System after Vaccination or Recovery from COVID-19?

“…For the Alpha variant, ChAdOx1 (University of Oxford-AstraZeneca), BNT162b2 (Pfizer-BioNTech) and Ad26.COV2.S (Janssen Pharmaceuticals) vaccines showed a slight effectiveness reduction, with 70%, 90% and 80% of protection, respectively [98][99][100]. For the Gamma variant, CoronaVac (Sinovac Research and Development) and Ad26.COV2.S (Janssen Pharmaceuticals) vaccines did not show significant reduction in protection [98,101]. Finally, concerning the Delta variant, it was shown that BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) vaccines did not elicit antibody neutralization responses against this variant, which demonstrated 6.8 times more resistance to neutralization [102].…”

SARS-CoV-2 variants in severely symptomatic and deceased persons who had been vaccinated against COVID-19 in São Paulo, Brazil

“…The estimated effectiveness was of 50.7% and 51.8% at two and three weeks after the second dose, respectively. Genomic sequencing of 142 samples found that 47% of the SARS-CoV-2 variants of concern (VOCs) were mostly gamma ( 7 ). However, the severity of confirmed COVID-19 cases was not considered, and the study was conducted before the gamma variant peaked in São Paulo.…”

Effectiveness of CoronaVac among healthcare workers in the setting of high SARS-CoV-2 Gamma variant transmission in Manaus, Brazil: A test-negative case-control study

“…31 However, these trials were conducted prior to the emergence of the Gamma variant. 31 Several preliminary studies have assessed the effectiveness of CoronaVac in other populations, including elderly individuals in São Paulo State, 32 HCWs in a single centre in São Paulo, 33 elderly age groups in Brazil, 34 and the general population in Chile. 31 More evidence is needed from observational studies conducted in Brazil and other countries where the Gamma variant or other lineages are circulating.…”