One dose of Covid-19 vaccine before first infection is associated with reduced risk of long-Covid, finds study – Irish Independent

The findings from the Swedish Covid-19 investigation for Future Insights is based on data for more than half a million Swedish adults, according to the British Medical Journal.

It shows unvaccinated individuals were almost four times as likely to be diagnosed with long-Covid than those who were vaccinated before first infection.

The researchers point out causality cannot be directly inferred from this observational evidence, but say their results highlight the importance of primary vaccination against Covid-19 to reduce the burden of the condition in the population.

The effectiveness of Covid-19 vaccines against the infection and severe complications of acute Covid-19 are already known, but their impact against long-Covid is less clear because most previous studies have relied on self-reported symptoms.

To address this, researchers investigated the effectiveness of primary Covid-19 vaccination the first two doses and the first booster dose within the recommended schedule against post-Covid-19 condition using data from the SCIFI-PEARL project, a register-based study of the pandemic in Sweden.

Individuals were followed from a first Covid-19 infection until a diagnosis of post-Covid-19 condition, vaccination, reinfection, death, emigration or end of follow-up.The average follow-up was 129 days in the total study population.

Individuals who had received at least one Covid-19 vaccine dose before infection were considered vaccinated.

A range of factors including age, sex, existing conditions, number of healthcare contacts, education level, employment status, and dominant virus variant at time of infection were also accounted for in the analysis.

Of 299,692 vaccinated people with Covid-19, 1,201 (0.4pc) were diagnosed with a post-Covid-19 condition during follow-up, compared to 4,118 (1.4pc) of 290,030 unvaccinated people.

Those who received one or more Covid-19 vaccines before the first infection were 58pc less likely to receive a diagnosis of post-Covid-19 condition than unvaccinated individuals.

And vaccine effectiveness increased with each successive dose before infection. For example, the first dose reduced the risk of post-Covid-19 condition by 21pc, two doses by 59pc, and three or more doses by 73pc.

These findings, combined with evidence from other studies, highlight the association between the immune system and the development of post-viral conditions, and underline the importance of timely vaccination during pandemics, say researchers in a linked editorial.

They call for continued investigation into the evolution of long-term residual symptoms of Covid-19 and other viral illnesses as well as steps to improve the accuracy of recording both recovery and continued illness after infection, and in quantifying key family, social, financial and economic outcomes.

Such estimates are fundamental to unlocking the funding required for future research and increased investment in specialist clinical services.

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One dose of Covid-19 vaccine before first infection is associated with reduced risk of long-Covid, finds study - Irish Independent