Lockdown measures and relative changes in the age-specific incidence of SARS-CoV-2 in Spain

Abstract

During the first months of the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) epidemic in 2020, Spain implemented an initial lockdown period on 15 March followed by a strengthened lockdown period on 30 March when only essential workers continued to commute to work. However, little is known about the epidemic dynamics in different age groups during these periods. We used the daily number of coronavirus 2019 cases (by date of symptom onset) reported to the National Epidemiological Surveillance Network among individuals aged 15-19 years through 65-69 years. For each age group g, we computed the proportion PrE(g) of individuals in age group g among all reported cases aged 15-69 years during the pre-lockdown period (1 −10 March 2020) and the corresponding proportion PrL(g) during two lockdown periods (initial: 25 March−3 April; strengthened: 8-17 April 2020). For each lockdown period, we computed the proportion ratios PR(g) = PrL(g)/PrE(g). For each pair of age groups g 1 , g 2 , PR(g 1)>PR(g 2) implies a relative increase in the incidence of detected SARS-CoV-2 infection in the age group g 1 compared with g 2 for the lockdown period vs. the pre-lockdown period. For the initial lockdown period, the highest PR values were in age groups 50-54 years (PR

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