Vaccination before Covid-19 infection significantly reduces risk of long covid

Covid-19 vaccination prior to infection significantly reduces the risk of developing post-covid-condition (PCC), commonly known as long covid, researchers reported on Nov. 22, 2023 in The BMJ/British Medical Journal.

“The results of this study suggest a strong association between covid-19 vaccination before infection and reduced risk of receiving a diagnosis of PCC. The findings highlight the importance of primary vaccination against covid-19 to reduce the population burden of PCC,” the authors said.

The purpose of the population-based Swedish study was to evaluate the prophylactic effect of primary covid-19 vaccination (first two doses and first booster dose within the recommended schedule) against postcovid-19 condition.

The 589,722 subjects were all adults, with covid-19 diagnoses first registered between December 27, 2020 and February 9, 2022. They were tracked from first infection until death, emigration, vaccination, reinfection, a postcovid-19 condition diagnosis or end of follow-up (30 November 2022), whichever happened first.

Subjects who had gotten one dose of a covid-19 vaccine before infection were deemed to have been vaccinated.

The primary endpoint was a clinical diagnosis of postcovid-19 condition.

They reported that, of 299,692 vaccinated subjects with covid-19, 1,201 (0.4%) received a diagnosis of postcovid-19 condition during follow-up. This compared with 4,118 (1.4%) of 290,030 unvaccinated subjects who developed postcovid-19 condition.

Those who had been vaccinated once or more prior to their first infection were 58% less likely to receive a diagnosis of post-covid-19 condition than unvaccinated subjects.

Notably, vaccine efficacy increased with each additional dose before infection. The first dose reduced the risk of post-covid-19 condition by 21%, two doses by 59%, and three or more doses by 73%.

The authors concluded, “The results from this study highlight the importance of complete primary vaccination coverage against covid-19, not only to reduce the risk of severe acute covid-19 infection but also the burden of post-covid-19 condition in the population.”