Abstract
Previous studies have indicated that antibody responses can be robustly induced after the vaccination in individuals previously infected by SARS-CoV-2. To evaluate anti-SARS-CoV-2 humoral responses in vaccinated individuals with or without a previous history of COVID-19, we compared levels of anti-SARS-CoV-2 antibodies in the sera from 21 vaccinees, including COVID-19-recovered or -naïve individuals in different times, before and after immunization with an inactivated COVID-19 vaccine. Anti-SARS-CoV-2-specific antibodies elicited after COVID-19 and/or immunization with an inactivated vaccine were measured by ELISA and Plaque Reduction Neutralizing assays. Antibody kinetics were consistently different between the two vaccine doses for naïve individuals, contrasting with the SARS-CoV-2-recovered subjects in which we observed no additional increase in antibody levels following the second dose. Sera from SARS-CoV2-naïve individuals had no detectable neutralizing activity against lineage B.1 SARS-CoV-2 or Gamma variant five months after the second vaccine dose. Contrarily, SARS-CoV-2-recovered subjects retained considerable neutralizing activity against both viruses. We conclude that a single inactivated SARS-CoV-2 vaccine dose may be sufficient to induce protective antibody responses in individuals with previous history of SARS-CoV-2 infection.
Highlights
All participants had blood collected at different timepoints before and after vaccination and tested by enzyme-linked immunosorbent assay (ELISA) against three distinct SARS-CoV-2 antigens
As of January 2022, almost a third of the 9.8 billion COVID-19 vaccine doses delivered globally corresponded to the inactivated vaccine made by Sinovac
Until May 2021, CoronaVac accounted for about 75% of the vaccine doses administered in Brazil this proportion has declined as the Brazilian vaccination rollout progressed [15]
Summary
The COVID-19 vaccine rollout has been decisive for curbing the SARS-CoV-2 pandemic. The mRNA BNT162b2/Pfizer and mRNA-1273/Moderna vaccines are based on messenger RNA, or mRNA, -targeting spike glycoprotein from SARS-CoV-2, responsible for the virus/cell attachment. This strategy indices the production of anti-spike antibodies, some of which are able to neutralize the virus by blocking spike binding to ACE2 receptor on type 2 alveolar cells. Non-replicative, recombinant adenoviruses were exploited on vaccines by University of Oxford/AstraZeneca and the Janssen Pharmaceuticals. Both are made up of adenovirus vectors encoding the S protein of SARS-CoV-2. It is expected that the surface spike protein is produced, encouraging the immune system to attack when it encounters the SARS-CoV-2 virus [4]
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