SARS-CoV-2 seroprevalence in Barcelona and Catalonia (Spain) after the 2020 lockdown

The study aimed to assess seroprevalence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Barcelona city (SRCOV2-BCN study) and the region of Catalonia, Spain (SRCOV2-CAT study) prior to the availability of coronavirus (COVID-19) vaccines. Humoral response to SARS-CoV-2 infection was assessed by detection of total antibodies (IgG, IgA and IgM) in surplus specimens from routine blood draw in the biochemistry laboratories of the participant hospitals. In Barcelona city, SARS-CoV-2 seroprevalence was 10.2% both in April and July 2020, without differences between men and women. The highest seroprevalence was found in individuals between 50 and 64 years old (13.7%). In Catalonia, SARS-CoV-2 seroprevalence in July 2020 was 9.2% and it was higher in women (10.1%) than in men (7.5%) (P = 0.0066), especially in the 50-64 age group (12.7% in women vs. 5.4% in men, P = 0.00051). The highest prevalence by age groups was 10%, found in individuals between 35 and 64 years old. Seroprevalence in the Barcelona province (11.7%) was higher than in the other provinces. In conclusion, SAR-CoV-2 seroprevalence in Catalonia during the first months of COVID pandemics was moderately high. There were differences by age, sex and geographical location that should be investigated.