In Sweden, University of Gothenburg researchers led an observational evaluation of the efficacy of primary COVID-19 vaccination (two doses followed by a booster) against long COVID among adults.

Of all participants vaccinated before infection, compared with the unvaccinated peers, a nearly four-fold difference was noticed(0.4% vs 1.4%).

In another study conducted in Pakistan, Aga Khan University researchers analyzed rates of persistent symptoms among 481 COVID-19-infected adults admitted to the university hospital from February to June 2021, with telephonic follow-up at 1 year.

Overall, 29.9% of patients had symptoms of long-term COVID-19, which were more common in those with severe or critical illness (35.5%) and the unvaccinated (37.9%).