Impact of scaling up SARS-CoV-2 vaccination on COVID-19 hospitalizations in Spain

Background: The advent of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines has been associated with a significant decline in coronavirus disease 2019 (COVID-19) hospitalizations and deaths. However, little is known about the benefits experienced by different population groups and/or using distinct vaccines. Methods: The Spanish public registry was analyzed to examine associations between weekly vaccination scale-up and the incidence of COVID-19 hospitalizations by age, sex, and vaccine modality. The study period extended from January 2020 to June 2021. Results: A total of 363 960 COVID-19 hospitalizations were recorded in Spain during the study period, with three peaks in March 2020, November 2020, and January 2021. The incidence of COVID-19 hospitalizations per 10 0 0 0 0 population increased exponentially with age, on average 71.5% for each decade older. Overall, individuals older than 60 years of age accounted for 65% of all COVID-19 hospitalizations. The speedy vaccination rollout since the end of 2020, with prioritization of the elderly groups, resulted in a rapid fall in COVID-19 hospitalizations starting in February 2021. The benefit was already noticed 3-4 weeks after the first dose, regardless of the vaccine modality. Conclusions: COVID-19 hospitalizations increased exponentially with age in all three peaks of SARS-CoV2 infection in Spain. Early mass vaccination of people over 60 years of age prevented a fourth wave of COVID-19 hospitalizations during the spring of 2021. (c) 2021 The Authors. Published by Elsevier Ltd on behalf of International Society for Infectious Diseases. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )

Automated summary

The study in Spain found that COVID-19 hospitalizations increased exponentially with age, with individuals over 60 years old accounting for 65% of all cases. The rapid vaccination rollout, especially prioritizing the elderly groups since the end of 2020, resulted in a sharp decline in COVID-19 hospitalizations starting in February 2021.