ABSTRACT
Different vaccines for SARS-CoV-2 are approved in various countries, but few direct comparisons of the antibody responses they stimulate have been reported. We collected plasma specimens in July 2021 from 196 Mongolian participants fully vaccinated with one of four Covid vaccines: Pfizer/BioNTech, AstraZeneca, Sputnik V and Sinopharm. Functional antibody testing with a panel of nine SARS-CoV-2 viral variant RBD proteins reveal marked differences in the vaccine responses, with low antibody levels and RBD-ACE2 blocking activity stimulated by the Sinopharm and Sputnik V vaccines in comparison to the AstraZeneca or Pfizer/BioNTech vaccines. The Alpha variant caused 97% of infections in Mongolia in June and early July 2021. Individuals who recover from SARS-CoV-2 infection after vaccination achieve high antibody titers in most cases. These data suggest that public health interventions such as vaccine boosting, potentially with more potent vaccine types, may be needed to control the COVID-19 pandemic in Mongolia and worldwide.
Subject(s)
COVID-19ABSTRACT
A surge in Covid-19 cases in Mongolia in March 2021 resulted in a government-mandated shutdown. This shutdown was relaxed in May 2021 as case numbers decreased and nationwide vaccination rates using Sinopharm, Covishield/AstraZeneca, Sputnik V, and Pfizer/BioNTech vaccines exceeded 50% of the population. Case rates increased again in early June 2021 in both vaccinated and non-vaccinated individuals. To determine whether the surge was due to the emergence of Delta or another variant, or vaccine failure, a rapid, opportunistic investigation was conducted that comprised virus sequence analysis of nasal swab samples from breakthrough cases and antibody assays of plasma from healthy vaccinees. More than 90% of breakthrough infections during the second case surge were due to the Alpha variant. Spike protein ELISA and SARS-CoV-2 neutralization assays data revealed large differences in plasma titers of antibodies to SARS-CoV-2, with mRNA vaccines eliciting higher titers than adenovirus-vectored or killed virus vaccines.