Covid immunity lasts at least a year after infection plus shots: Study

People who have been both previously infected and vaccinated against Covid-19 get long-lasting protection against severe disease and hospitalization, a large international study found.

The combination prevented more than 97 per cent of severe disease or hospitalization for up to 12 months after infection or initial immunization, whichever was most recent, according to a report from the World Health Organization. Boosters conferred an additional 6 months of protection. Meanwhile, infection alone was just under 75 per cent protective over a year.  

The report was based on a review of more than two dozen studies from January 2020 to June 2022 on protection afforded by hybrid immunity and by previous infection alone. The findings should be used to tailor guidance on the number and timing of Covid shots, the report said.

Scheduling for updated booster shots has long been debated among health experts who disagree on intervals between vaccine doses and whether updated boosters are necessary for all age groups. The US Food and Drug Administration staff is set to meet Jan. 26 with a group of outside advisers to discuss whether immunization policies should be revised as the pandemic evolves.