Seroprevalence of SARS-CoV-2 antibodies in vaccinated healthcare workers in Marrakech (Morocco)

Introduction: The SARS-CoV-2 pandemic has had a considerable impact, causing millions of deaths worldwide, including many healthcare workers (HCWs). The pharmaceutical industry has been working diligently since the start of the pandemic to develop various vaccines to fight the spread of the virus and protect the population. Objective: To study the seroprevalence of neutralizing anti-SARS-CoV-2 antibodies in vaccinated HCWs at the Mohamed VI University Hospital in Marrakech and to determine the parameters that can influence immune response. Methods: A cross-sectional study of 138 HCWs was performed between October and December 2021 by measuring IgG antibodies directed against the spike antigen of SARS-CoV-2 using an Abbott Architect (R) SARS-CoV-2 IgG II assay. Results: The mean age was 31.42 years, the sex ratio was 2.94 women to each man, and the overall prevalence was 97%. We found 39.5% of the participants had experienced COVID-19 infections pre-vaccination, which decreased to 26.8% after vaccination. Neutralizing antibody titers were dependent on the type of vaccine: they were higher with the PfizerBioNTech vaccine, the number of doses (p < .001), and post-vaccine COVID-19 form. The post-vaccine COVID-19 infection rates were lower with the Sinopharm vaccine. Conclusion: Heterologous vaccination with non-mRNA and mRNA vaccines and the consideration of post-vaccination COVID-19 infection as a booster could help optimize vaccine results while reducing potential side effects.