The first months of the SARS-CoV-2 epidemic in Spain resulted in high incidence and mortality. Little is known about the epidemic dynamics in different age groups, including the relative effect of the lockdown measures introduced on March 15, and strengthened on March 30 to April 14, 2020 when only essential workers continued to work. Miguel Hernan, Kolokotrones Professor of Biostatistics and Epidemiology, Research Fellow Pablo Martinez de Salazar Munoz, and senior research Scientist Ed Goldstein used data from the National Epidemiological Surveillance Network (RENAVE in Spanish) on the daily number of reported COVID-19 cases (by date of symptom onset). For each age group they computed the proportion of individuals in each age group among all reported cases aged 15-69y during the pre-lockdown period (March 1-10, 2020) and the corresponding proportion during two lockdown periods (March 25-April 3 and April 8-17, 2020). For each lockdown period they computed the proportion ratios. The proportion ratio for the later vs. early period was used for describing a relative increase/decrease in the incidence of detected SARS-CoV-2 infection.
Their results suggest that different outbreak control measures led to different changes in the relative incidence by age group. During the first lockdown period, when non-essential work was allowed, individuals aged 40-64y, particularly those aged 50-59y presented with higher COVID-19 relative incidence compared to pre-lockdown period, while younger adults/older adolescents (together with persons aged 50-59y) had increased relative incidence during the later, strengthened lockdown. The role of different age groups during the epidemic should be considered when implementing future mitigation efforts.
Relevant links: https://www.medrxiv.org/content/10.1101/2020.06.30.20143560v1