Risk of infection, hospitalization, and death up to 9 months after a second dose of COVID-19 vaccine: A retrospective, total population cohort study in Sweden
The Lancet — Nordström P, Ballin M, Nordström A, et al. | February 08, 2022
Using data from Swedish nationwide registers, researchers conducted this retrospective, total population cohort study investigating the effectiveness of COVID-19 vaccination against the risk of infection, hospitalization, and death during the first 9 months after vaccination for the total population of Sweden.
Researchers retrieved data of 842,974 individuals who were fully vaccinated (two doses), and matched them (1:1) to an equal number of unvaccinated individuals (total study cohort n = 1,685,948).
Vaccine effectiveness against SARS-CoV-2 infection of any severity progressively waned across all subgroups, but there were differences in the rate of waning according to vaccine type.
Vaccine effectiveness appeared to be better maintained with respect to severe COVID-19, although there was some waning after 4 months.
These results yield support for administration of a third vaccine dose as a booster.
Read the full article on The Lancet