This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
Researchers analysed data on more than 20 million adults. They found that, compared to those who had not had a COVID-19 vaccine, people who were vaccinated had a lower risk of:
- long COVID
- blood clots and heart failure following infection with COVID-19.
More information on long COVID can be found on the NHS website.
The issue: do COVID-19 vaccines protect against long COVID?
People have long COVID if their symptoms continue for 3 months or more after the initial infection. In March 2023, 1.9 million people in the UK reported they had long COVID. Symptoms include tiredness, difficulty breathing, and brain fog (problems with concentration), and can severely harm people’s quality of life.
COVID-19 vaccines protect against infection and severe illness, but their effect on long COVID is less clear. This study assessed whether COVID vaccines protect against long COVID.
What’s new?
The researchers analysed data on approximately 10 million vaccinated, and 10 million unvaccinated, adults from the UK, Spain, and Estonia. They used primary care databases for the UK and Spain and a health insurance database for Estonia.
Vaccination started in January 2021 but the date of people’s first vaccination depended on their country and eligibility. Both groups (vaccinated and unvaccinated) were followed up until December 2021 – December 2022 depending on the database or until they died, had a second vaccine (or a first if unvaccinated) or left the GP practice (or insurance company) which provided their data. The researchers adjusted results for age, date, health conditions, and location.
The main outcome was the number of people who had a long COVID symptom (of the 25 recognised by the World Health Organisation) 3 – 12 months after a positive test for COVID-19 (and no history of the symptom 180 days before their COVID infection).
The researchers found that:
- the vaccinated group were 29 – 52% less likely to develop long COVID than the unvaccinated group
- the findings were consistent across the countries and databases analysed.
In a related study, the researchers examined the risk of cardiovascular complications following COVID-19 infections. Compared with unvaccinated people, up to 180 days after vaccination, people were:
- 53% less likely to develop a blood clot in a vein
- 72% less likely to develop a blood clot in an artery
- 61% less likely to develop heart failure.
Why is this important?
This was the first international study to show that COVID-19 vaccines reduce the risk of long COVID at a population level. This information provides further support for the benefits of COVID-19 vaccines.
Concerns have been raised that COVID-19 vaccines could increase the risk of inflammation of the heart and its lining. These findings provide reassurance that vaccines protect against cardiovascular complications after COVID infections.
The researchers hope that, in any future wave of the COVID-19 pandemic, their findings will encourage vaccination among adults who have never been vaccinated. They say this is particularly important for those who were hesitant because they thought they were at low risk of severe COVID-19 (typically young, healthy, fit people) or afraid of side effects (such as blood clots or heart problems).
This study looked at symptoms that were serious enough to be reported to a GP. Therefore, less serious symptoms of long COVID may have been missed.
What’s next?
The European Medicines Agency discussed these results at the European Pandemic Emergencies Task Force. The researchers suggest that their findings could inform future pandemic responses, and future research into this and similar topics.
The researchers caution that the effectiveness of vaccines fade over time. Therefore, the long-term effectiveness of vaccines against long COVID needs to be investigated.
You may be interested to read
This is a summary of: Català M, and others. The effectiveness of COVID-19 vaccines to prevent long COVID symptoms: staggered cohort study of data from the UK, Spain, and Estonia. Lancet Respiratory Medicine 2024; 12: 225 – 236.
The related cardiovascular study: Mercadé-Besora, N and others. The role of COVID-19 vaccines in preventing post-COVID-19 thromboembolic and cardiovascular complications. Heart 2024; 110: 635 – 643.
Another study showing vaccines reduce the risk of cardiovascular problems after COVID-19 infection: Cezard GI, and others. Impact of vaccination on the association of COVID-19 with cardiovascular diseases: An OpenSAFELY cohort study. Nature Communications 2024; 15: 1 - 14.
A related study with similar findings from Norway: Trinh NTH, and others. Effectiveness of COVID-19 vaccines to prevent long COVID: data from Norway. Lancet Respiratory Medicine 2024; 12: e33 – e34.
A podcast about the study from Lancet Respiratory Medicine.
A video discussing the trial by the researchers.
An NIHR and Guardian article about the cardiovascular study.
A British Heart Foundation article on long COVID tests, treatment, and support.
A World Health Organisation article on the benefits and safety of COVID vaccines.
Information on taking part in NIHR research on long COVID.
Funding: This study was funded by the NIHR Oxford Biomedical Research Centre.
Conflicts of Interest: Several authors have received fees and funding from pharmaceutical companies. See paper for full details.
Disclaimer: Summaries on NIHR Evidence are not a substitute for professional medical advice. They provide information about research which is funded or supported by the NIHR. Please note that the views expressed are those of the author(s) and reviewer(s) at the time of publication. They do not necessarily reflect the views of the NHS, the NIHR or the Department of Health and Social Care.
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