People vaccinated against Covid-19 have less chance of developing long Covid in the event of an infection, a study suggests.
The UK Health Security Agency data review also indicates that being inoculated may alleviate symptoms in those who are already experiencing long Covid symptoms.
Researchers studied evidence taken from 15 studies of the condition and how it is affected by vaccination.
Two of these studies found that fewer fully vaccinated people developed the medium or long-term symptoms associated with long Covid, such as headaches, fatigue and dizziness.
“There is also evidence that unvaccinated people with long Covid who were subsequently vaccinated had, on average, reduced long Covid symptoms, or fewer long Covid symptoms than those who remained unvaccinated,” the review said.
While a link between vaccination and reduced long Covid symptoms has been established, the reason for the relationship has not – although various theories have been postulated.
One is that the vaccine expunges all fragments of the virus in the system that lead to ongoing inflammation. Another is that it acts as an immune counterbalance in people whose symptoms have an autoimmune aetiology.
The latter hypothesis might explain why some people in the studies actually experienced worse long Covid symptoms after being vaccinated, according to Deborah Dunn-Walters, chair of the British Society for Immunology Covid-19 taskforce and a professor of immunology at the University of Surrey.
This cohort are relative outliers, however, and Prof Dunn-Walters is in no doubt as to the takeaway message from the review.
"[It} re-emphasises the importance of everyone, no matter their age, getting vaccinated against Covid-19," she said.
"Although there has been a high uptake of the vaccines in the UK so far, a significant number of people still need to come forward for a first or second dose. We must continue to make every effort to reach these people and encourage them to come forward for Covid-19 vaccination.”
Her rallying call was echoed by Prof Stephen Powis, the national medical director of NHS England.
“With more than 10,000 people in hospital with Covid [in the UK], this study is a timely and important reminder that vaccines remain our best protection against the virus, reducing the chances of becoming seriously unwell as well as the effects of long Covid,” he said.