The second round of a population-based seroprevalence study of
anti-SARS-CoV-2 antibodies and the assessment of COVID-19 vaccination in
the Republika Srpska, Bosnia and Herzegovina
Abstract
Introduction: The aim of the study was to assess the seroprevalence of
SARS-CoV-2 in the Republika Srpska, Bosnia and Herzegovina, after five
waves of COVID-19 and one year after introduction of vaccination to
better understand the true extent of the COVID-19 pandemic and role of
vaccination in achieving herd immunity. Methods: The population-based
study was conducted from December 2021 to February 2022 in a group of
4,463 individuals from the Republika Srpska. Total anti-SARS-CoV-2
antibodies were determined in serum specimens using the Wantai total
antibody ELISA assay and Kantaro Quantitative IgG assays. Results: The
overall cumulative seroprevalence was 94.6%. Of all participants,
61.3% were vaccinated against COVID-19. Significantly higher
seroprevalence rates were observed among vaccinated participants. Among
various professions, the highest seroprevalence was found in the service
industry (98.1%), education (98.0%) and healthcare (96.9%). This
study found that 2.2% of vaccinated participants, and 3.6% of
individuals with SARS-CoV-2 positivity during 2021, had no detectable
IgG antibodies. Both seroprevalence and antibody titres were
significantly higher in people with hybrid immunity. Conclusion: Our
findings reveal a 2,3-fold increase in seroprevalence of SARS-CoV-2
antibodies due to infection and vaccination, comparing to the first
study performed one year earlier. This study provides better
understanding of the SARS-CoV-2 transmission and highlights the
important role of the vaccination in achieving the population immunity.
Periodically conducted population-based seroprevalence studies are
important for assessment of surveillance system performance and public
compliance with vaccination policies. Keywords: COVID-19, SARS-CoV-2
antibodies, seroprevalence, population-based study, Bosnia and
Herzegovina, UNITY, SEROPREV.