A large study led by researchers from King’s College London has found fully vaccinated adults are around 50 percent less likely to suffer from long COVID if they are unfortunate enough to experience a breakthrough SARS-CoV-2 infection.
The new research comes from a huge ongoing project called the Zoe COVID Symptom Study, which was launched early in 2020 and involves the general public downloading an app to provide daily COVID status reports.
So far more than 4.7 million people have downloaded the app, delivering researchers an unprecedented volume of data.
This latest analysis of Zoe data, published in The Lancet Infectious Diseases, looked at the characteristics of COVID-19 infections in a large cohort of vaccinated individuals.
Data from nearly one million fully vaccinated subjects was analyzed in the new research. Compared to unvaccinated controls, the research found vaccinated individuals experiencing a breakthrough COVID-19 infection were 49 percent less likely to report symptoms lasting longer than 28 days.
The research also looked at the characteristics of COVID-19 infections in vaccinated individuals. While vaccinated individuals experienced similar COVID-19 symptoms, such as cough, fever and headaches, they reported milder symptoms compared to unvaccinated subjects. Vaccinated subjects were also significantly less likely to experience multiple symptoms in the first week of an infection.
“Vaccinations are massively reducing the chances of people getting long COVID in two ways,” explains Tim Spector, lead investigator on the Zoe COVID study. “Firstly, by reducing the risk of any symptoms by eight to 10 fold and then by halving the chances of any infection turning into long COVID, if it does happen. Whatever the duration of symptoms we are seeing that infections after two vaccinations are also much milder, so vaccines are really changing the disease and for the better.”
The findings also offer a reminder of the importance of getting a second vaccine dose for effective protection. Frail older adults were found to still be at significant risk of COVID-19 infection after one vaccine dose, and even after full vaccination this vulnerable cohort was twice as likely to get sick from a breakthrough infection.
Clare Steves, a King’s College London researcher working on the study, says this is an important reminder for those in high-risk cohorts to get that second dose, and potentially booster shots when they become available.
“In terms of the burden of long COVID, it’s good news that our research has found that having a double vaccination significantly reduces the risk of both catching the virus and if you do, developing long-standing symptoms,” says Steves. “However, among our frail, older adults and those living in deprived areas the risk is still significant and they should be urgently prioritized for second and booster vaccinations.”