SARS-CoV-2 neutralizing antibody response in vaccinated and non-vaccinated hospital healthcare workers with or without history of infection.

Between March 2021 and February 2022, SARS-CoV-2 neutralizing antibodies dynamics was investigated in a prospective observational study in 903 healthcare workers of a hospital in Switzerland. A surrogate neutralization assay measuring the competitive inhibition of the angiotensin converting enzyme 2 (ACE2) binding to the spike protein (S) of the SARS-CoV-2 wild type virus and to five variants of concern (Alpha, Beta, Gamma, Delta, Omicron) was used. We observed a broad distribution of neutralization activity among participants and substantial differences in neutralizing titers against variants. Participants were grouped based on combinations of vaccination status (1, 2 or 3 doses) and/or prior or subsequent SARS-CoV-2 infection/reinfection. Triple vaccination resulted in the highest neutralization response, as did double vaccination with prior or subsequent infection. Double vaccination without infection showed an intermediate neutralization response while SARS-CoV-2 infection in non-vaccinated participants resulted in poor neutralization response. After triple vaccination or double vaccination plus infection, additional vaccination and/or reinfection had no impact on neutralizing antibody titers over the observed period. These results strongly support the booster dose strategy, while additional booster doses within short time intervals might not improve immunization. However, dynamics of neutralizing antibodies titers needs to be monitored individually, over time and include newly emerging variants.

SARS-CoV-2 seroprevalence in hospital healthcare workers in Western Switzerland at the end of the second pandemic wave.

Introduction. In early January 2020, the pandemic of COVID-19 (coronavirus disease 2019) rapidly spread from China and caused a worldwide pandemic.Hypothesis. Healthcare workers represent a high-risk group for acquiring COVID-19 and for nosocomial transmission of severe acute respiratory coronavirus 2 (SARS-CoV-2).Aim. We aimed to investigate over a 1 year period, across two pandemic waves, the SARS-CoV-2 seroprevalence in employees at a Western Switzerland public hospital.Methodology. A prospective observational SARS-CoV-2 seroprevalence study was proposed to all hospital employees who enrolled on a voluntary basis.Results. Out of 594 participants recruited on a voluntary basis, 269 volunteers (45.3 %) had anti-SARS-CoV-2 antibodies: this seroprevalence was twice higher than that reported in the local community. Healthcare workers with prolonged exposure to patients with COVID-19 showed a significantly higher odds ratio (OR) of having a positive SARS-CoV-2 serology [OR 3.19, 95 % confidence interval (CI) 2.16-4.74]. Symptoms showing the highest association with a positive serology were anosmia (OR 11.9, 95 % CI 5.58-30.9) and ageusia (OR 10.3, 95 % CI 4.8-26.3). A total of 17.1 % (95 % CI 12.2-21.1 %) of SARS-CoV-2 seropositive volunteers did not report a suspicion of COVID-19 in their personal history.Conclusion. Overall, we observed that the impact of the second SARS-CoV-2 pandemic wave was considerable and significantly affected healthcare workers with prolonged exposure to patients with COVID-19.