Long COVID: double vaccination halves risk of developing long-lasting symptoms

In unvaccinated people, around one in 20 who get symptomatic COVID-19 experience symptoms for at least eight weeks. Around one in 50 have symptoms that drag out for three months or more.

We wanted to know whether COVID-19 vaccines might protect against developing long-lasting symptoms. To find out, we looked at data provided by more than a million regular contributors to the COVID Symptom Study, a project in which members of the public log their symptoms via an app to help with research.

Our latest analysis of the study’s data, covering around 2 million vaccine doses, shows that vaccines significantly reduce the risk of catching COVID-19, with only 0.2% of those fully vaccinated later testing positive for the virus.

Even if you’re unlucky enough to catch the virus after being vaccinated, your chances of falling seriously ill or dying are slashed. Double-vaccinated people are 31% less likely to experience acute COVID-19 symptoms and 73% less likely to be hospitalised – a result that’s borne out in the relatively low hospitalisation and death rates we’re seeing now even as tens of thousands of people are still testing positive every day in the UK.

Reassuringly, for those who did fall ill with COVID-19 after being vaccinated, only around 5% went on to have symptoms that lasted for more than four weeks, meaning their chances of developing long COVID were cut by half. One of the best ways to reduce your risk of getting long COVID is to get fully vaccinated as soon as possible.

However, we did notice that frail older people and those living in more socially deprived areas were more likely to be infected and fall ill with COVID-19 after being vaccinated, especially if they had only had one vaccine dose. This suggests that we should prioritise further vaccination efforts and public health measures such as masking and social distancing among these groups, especially where infection rates are high and people are mixing and moving around.

Vaccines and long COVID

As the UK vaccination programme rolled out, we also started to notice anecdotal reports from people living with long COVID that their symptoms seemed to improve after being vaccinated.

The patient-led LongCovidSOS group chose to investigate this by surveying over 800 long COVID patients early in 2021. More than half of those surveyed noticed an overall improvement in their symptoms after vaccination, which then appeared to be sustained in about half of this group. Around a quarter of the overall respondents reported no difference and one-fifth said their symptoms had got worse. These findings have been released as a preprint, so haven’t yet been reviewed by other scientists, but they’ve been backed up by data from the COVID Symptom Study, which we’ll be publishing soon.

However, while there does seem to be some kind of link between receiving a COVID-19 vaccine and improvements in long COVID, it’s not clear exactly how the two are connected. It could be that the immune response triggered by the vaccine has a direct impact on symptoms.

Alternatively, it could just be that time has continued to pass since these people were originally infected and they’re experiencing a natural recovery from the virus. Or it could be a bit of both. Either way, more research is needed to tease out what’s going on.

What we can say is that COVID-19 vaccines certainly aren’t harmful for people with long COVID. What’s more, because we know that it’s possible to be reinfected with the virus, there’s a risk that catching it a second time could exacerbate symptoms for people living with long COVID and set them back even further. It’s therefore vital that we encourage anyone with long COVID who has not been vaccinated to do so as soon as possible, to help protect themselves and those around them.

A serious threat

Although the chances of developing long COVID after being vaccinated are small, this is a numbers game and a small percentage of a big number can still be substantial. As long as we are seeing tens of thousands of cases every day, we can still expect to see a substantial number of people living with lingering symptoms over the coming months.

This is particularly important for younger people, who may be less worried about hospitalisation or death, yet who can still be susceptible to the debilitating long-term effects of the virus. A lot can happen in a few months when you’re young, and long COVID can mean that people miss out on life-changing opportunities, like sitting an exam or taking up a new job, as well as the social activities that bring joy and wellbeing to life.

We’ll probably all be living with COVID-19 for some time to come. But with a combination of vaccination and public health measures where necessary, we can help to make sure that as few people as possible have to directly live with its life-limiting long-term effects.

Claire Steves consults for ZOE Ltd which is the company which developed the COVID Symptom Study together with King's College London. She receives funding from the Medical Research Council, the National Institute for Health Research, the Wellcome Trust and Chronic Disease Research Foundation.