Being vaccinated against COVID-19 halves people’s risk of developing long COVID, according to new research from the University of East Anglia.

The research, published in JAMA Internal Medicine, sought to determine which factors might make people more or less susceptible to developing long COVID. The team looked at data from 41 studies around the world involving 860,783 patients.

“Long COVID is a complex condition that develops during or after having COVID, and it is classified as such when symptoms continue for more than 12 weeks,” says Vassilios Vassiliou, PhD, from Norwich Medical School and honorary consultant cardiologist at the Norfolk and Norwich University Hospital, in a press release. “Just over 2 million people in the UK are thought to suffer with long COVID, and it affects people in different ways.”

Breathlessness, a cough, heart palpitations, headaches, and severe fatigue are among the most prevalent symptoms of the condition, notes Vassiliou. Other symptoms may include chest pain or tightness, brain fog, insomnia, dizziness, joint pain, depression and anxiety, tinnitus, loss of appetite, headaches, and changes to sense of smell or taste.

As far as risk factors, researchers found that female sex, older age, increased BMI, and smoking are associated with an increased risk of long COVID, as well as co-morbidities such as asthma, COPD, type 2 diabetes, coronary heart disease, immunosuppression, anxiety, and depression. Furthermore, severe illness during the acute phase, as reflected by the need for hospitalization or admission to an intensive care unit, is also associated with the development of long COVID.

Conversely, researchers found that people who had been vaccinated had significantly less risk, almost half the risk, of developing long COVID compared to unvaccinated participants.

“These findings are important because they enable us to better understand who may develop long COVID and also advocate for the benefit of vaccination,” says Vassiliou in a press release.

Co-author Dr Eleana Ntatsaki from UCL and Ipswich Hospital says in a press release, “Our findings help define the full demographic characteristics and the risk factors for developing long COVID. We can now better understand and serve this population with long-term care planning, support for long COVID clinics, and increase awareness of the prevalence and impact of the condition. Furthermore, we can have a better strategy for optimizing any modifiable risk factors, with public health promotion campaigns, encouraging smoking cessation, vaccination, and healthy weight management in the target population.”

The research was led by the University of East Anglia in collaboration with the Norfolk and Norwich University Hospital, Imperial College London and Imperial College Healthcare NHS Trust, Cambridge University Hospitals, Ipswich Hospital, and University College London.