Vaccination against Covid-19 also protects against long Covid, a UK Health Security Agency (UKHSA) rapid evidence review has concluded.

Researchers identified 15 UK and international studies which reported on the effectiveness of vaccination against long Covid, with seven looking at the impact of vaccination before infection, seven looking at the effect of vaccination in unvaccinated people with long Covid and one examining both.

An Office for National Statistics survey published last month found an estimated 1.3 million people in the UK had long Covid.

Most of the eight studies looking at the effect of vaccination before infection in the latest UKHSA review suggested that vaccinated people (with one or two doses) were less likely to develop symptoms of long Covid following infection compared with unvaccinated people – in the short term and long term (4 weeks to 6 months after infection).

For example, data showed that people with Covid-19 who received two doses of the Pfizer, AstraZeneca, or Moderna vaccines or one dose of the Janssen vaccine, were about half as likely as people who received one dose or were unvaccinated to develop long Covid symptoms lasting more than 28 days.

There was also evidence that vaccine effectiveness against most post-Covid symptoms was highest in people aged 60 years and over and lowest for younger participants aged 19 to 35 years.

The review authors noted that the studies only included people who had developed Covid so did not account for the cases where vaccination had prevented infection, meaning they underestimated the effectiveness of vaccines to prevent long Covid.

Examining the eight studies looking at long Covid in unvaccinated people, there was some evidence that those who were subsequently vaccinated had, on average, reduced long Covid symptoms, although the review authors noted some people reported worsened symptoms after vaccination.

‘Additionally, there was evidence that unvaccinated people with long Covid who were subsequently vaccinated reported fewer long Covid symptoms than those who remained unvaccinated,’ the review authors concluded.

Acknowledging the review’s limitations, the authors said all the studies were observational and there a risk of bias due to differences between people who were vaccinated and unvaccinated, how outcomes were measured and participant selection.

Commenting on the findings, Professor Deborah Dunn-Walters, chair of the British Society for Immunology Covid-19 Taskforce and professor of immunology at the University of Surrey, said the comprehensive review reinforced the need for everyone to take up the offer of Covid-19 vaccination.

‘The term ‘long Covid’ covers a wide range of post-Covid conditions and so we don’t yet fully understand all the processes involved,’ she said. 

‘The immune system is thought to play a role in symptom development in a significant number of cases, likely as a result of an over-reactive and/or slightly misdirected immune response during the acute Covid infection.’

Although there had been a high uptake of the vaccines in the UK so far, a significant number of people still needed 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,’ she said.