Do vaccines affect long covid?14 Aug 2021 21:35
From New Scientist article 14/7/21:
Being vaccinated reduces your chance of getting long covid, which can involve a variety of symptoms that persist for weeks or months after an infection with coronavirus.
The benefits of vaccination in reducing the risk of getting long covid can be seen even if people get infected after having a shot. There is also evidence that vaccines reduce the severity of symptoms in most people who already have long covid, but in a minority their symptoms worsen.
While various studies are getting under way, so far there is almost no published evidence on the relationship between long covid and vaccination.
“We do not yet know to what extent covid-19 vaccination can prevent long covid,” says Annika Jödicke at the University of Oxford, whose team will use data from the UK’s National Health Services to try to answer this question.
A team at King’s College London has released initial findings from an ongoing study in which people report any long covid symptoms via an app. According to study leader Tim Spector, vaccination reduces the risk of getting long covid by a factor of 20 (medRxiv, doi.org/gk7czd). This is mainly because vaccination reduces the risk of being infected in the first place by a factor of 10, and the risk is also halved in those who get infected despite being vaccinated, says Spector.
For those who already have long covid, it seems vaccination can be helpful. In a survey of 900 people who were vaccinated after having symptoms lasting for at least four weeks and in most cases more than three months, around 60 per cent reported an overall improvement in their symptoms. A quarter reported no difference and 20 per cent reported worsened symptoms (SSRN, doi.org/gqrw).
“Ours is the largest study and probably the best evidence to date,” says Ondine Sherwood at LongCovidSOS, a UK organisation that campaigns for support for people with long covid.
Of the three vaccines that Sherwood and her colleagues assessed, the Moderna one was most beneficial, reducing the average symptom severity score by 31 per cent. For Pfizer/BioNTech, it was 24 per cent, and 23 per cent for Oxford/AstraZeneca.
Sherwood and her team want to do a follow-up to see how long the symptoms last and what the impact of a second dose is. However, a randomised trial rather than a survey would provide more reliable results.
The different effects of vaccination on long covid make sense given emerging evidence that there are many different mechanisms that can cause long covid. It can be due, for instance, to persistent infections in some parts of the body, to tissue damage from past infection, to disruption of the immune system or can arise from all of these occurring in one person.
Vaccines would be expected to help clear persistent infections, but to make no difference to tissue damage. They might even worsen immune disruption in some cases.
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