SARS-CoV-2 Seroprevalence and Antibody Kinetics Among Health Care Workers in a Spanish Hospital After 3 Months of Follow-up
Gemma Moncunill, Alfredo Mayor, Rebeca Santano, Alfons Jiménez, Marta Vidal, Marta Tortajada, Sergi Sanz, Susana Méndez, Anna Llupià, Ruth Aguilar, Selena Alonso, Diana Barrios, Carlo Carolis, Pau Cisteró, Eugenia Chóliz, Angeline Cruz, Sílvia Fochs, Chenjerai Jairoce, Jochen Hecht, Montserrat Lamoglia, Miguel J. Martínez, Javier Moreno, Robert A. Mitchell, Natalia Ortega, Núria Pey, Laura Puyol, Marta Ribes, Neus Rosell, Antía Figueroa-Romero, Patricia Sotomayor, Sara Torres, Sarah Williams, Sónia Barroso, Anna Vilella, Antoni Trilla, Pilar Varela, Carlota Dobaño, Alberto L. García‐Basteiro
Abstract
BACKGROUND: At the COVID-19 spring 2020 pandemic peak in Spain, prevalence of SARS-CoV-2 infection in a cohort of 578 randomly selected health care workers (HCWs) from Hospital Clínic de Barcelona was 11.2%. METHODS: A follow-up survey 1 month later (April-May 2020) measured infection by rRT-PCR and IgM, IgA, and IgG to the receptor-binding domain of the spike protein by Luminex. Antibody kinetics, including IgG subclasses, was assessed until month 3. RESULTS: At month 1, the prevalence of infection measured by rRT-PCR and serology was 14.9% (84/565) and seroprevalence 14.5% (82/565). We found 25 (5%) new infections in 501 participants without previous evidence of infection. IgM, IgG, and IgA levels declined in 3 months (antibody decay rates 0.15 [95% CI, .11-.19], 0.66 [95% CI, .54-.82], and 0.12 [95% CI, .09-.16], respectively), and 68.33% of HCWs had seroreverted for IgM, 3.08% for IgG, and 24.29% for IgA. The most frequent subclass responses were IgG1 (highest levels) and IgG2, followed by IgG3, and only IgA1 but no IgA2 was detected. CONCLUSIONS: Continuous and improved surveillance of SARS-CoV-2 infections in HCWs remains critical, particularly in high-risk groups. The observed fast decay of IgA and IgM levels has implications for seroprevalence studies using these isotypes.