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 LancetNordström 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