Direct and Indirect Effectiveness of mRNA Vaccination against Severe Acute Respiratory Syndrome Coronavirus 2 in Long-Term Care Facilities, Spain

Abstract

We conducted a registries-based cohort study of long-term care facility residents >65 years of age offered vaccination against severe acute respiratory syndrome coronavirus 2 before March 10, 2021, in Spain. Risk for infection in vaccinated and nonvaccinated persons was compared with risk in the same persons in a period before the vaccination campaign, adjusted by daily-varying incidence and reproduction number. We selected 299,209 persons; 99.0% had >1 dose, 92.6% had 2 doses, and 99.8% of vaccines were Pfizer/BioNTech (BNT162b2). For vaccinated persons with no previous infection, vaccine effectiveness was 81.8% (95% CI 81.0%-82.7%), and 11.6 (95% CI 11.3-11.9) cases were prevented per 10,000 vaccinated/day. In those with previous infection, effectiveness was 56.8% (95% CI 47.1%-67.7%). In nonvaccinated residents with no previous infection, risk decreased by up to 81.4% (95% CI 73.3%-90.3%). Our results confirm vaccine effectiveness in this population and suggest indirect protection in nonvaccinated persons.

Keywords: COVID-19; SARS-CoV-2; Spain; coronavirus disease; elderly; indirect effects; long-term care facilities; respiratory infections; severe acute respiratory syndrome coronavirus 2; transmissibility; vaccination; vaccine effectiveness; viruses; zoonoses.

Figure 1

Seven-day cumulative incidence of diagnosis of severe acute respiratory syndrome coronavirus 2, Spain. Shadowed areas indicate the study period for the selected persons (December 27, 2020–March 10, 2021) and the reference period 87 days before (October 1–December 13, 2020).

Figure 2

Cumulative incidence of documented severe acute respiratory syndrome coronavirus 2 infection in long-term care facilities estimated from adjusted hazards models, Spain, December 27, 2020–March 10, 2021. A) Standardized risk in the vaccinated with no previous infection and its reference group; B) standardized risk in the vaccinated with previous infection and its reference group; C) standardized risk in nonvaccinated (indirectly protected) with no previous infection and its reference group; D) standardized risk in nonvaccinated (indirectly protected) with previous infection and its reference group. Solid lines indicate study group; dotted lines indicate reference group.