Having at least one dose of Covid-19 vaccine before a first infection is strongly linked to a lower risk of developing long Covid, say Swedish researchers.
There also appears to be a dose response effect with subsequent doses offering even more protection, they reported.
Analysis of data from half a million adults showed that unvaccinated people were almost four times more likely to be diagnosed with long Covid than those who had been jabbed before they were infected.
Writing in the BMJ, the researchers noted their work could not prove causality but did ‘highlight the importance of primary vaccination against covid-19 to reduce the burden of post-covid-19 condition in the population’.
The study also took into account a range of other factors including age, sex, existing medical conditions, number of healthcare contacts in the year before the pandemic, education level, employment status, and dominant virus variant at time of infection.
Their analysis found that of 299,692 vaccinated individuals with Covid-19, 1,201 (0.4%) were diagnosed with what the researchers called post-covid-19 condition during follow-up, compared with 4,118 (1.4%) of 290,030 unvaccinated individuals.
People who had one or more Covid-19 vaccines before their first infection were 58% less likely to be diagnosed with a long Covid condition than unvaccinated individuals.
The researchers also found that vaccine effectiveness increased with each successive dose before infection with the first dose cutting the risk of long Covid by 21%, two doses by 59%, and three or more doses by 73%.
They 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.’
Steps also need to be taken to ‘improve the accuracy of recording both recovery and continued illness after infection, and in quantifying key family, social, financial, and economic outcomes’, they added.
‘Future pandemic preparedness plans should continue to prioritise prompt manufacture, evaluation, and distribution of vaccines, and mass vaccination to reduce a pandemic’s impact on health,’ they concluded.