People who have been vaccinated against COVID-19 have a significantly lower risk of being diagnosed with Post-COVID Condition after COVID-19 infection, according to a study at the University of Gothenburg. The researchers emphasize the importance of vaccination to reduce human suffering and pressure on healthcare services.
The study, published in the journal BMJ, includes all registered cases among adults who contracted COVID-19 for the first time between December 27, 2020 and February 9, 2022 in Sweden's two largest healthcare regions, Stockholm and Västra Götaland. A total of 589,722 people were included and followed up using register data.
Just over half of them - 51% - had been given one or more doses of vaccine before contracting COVID-19, while the other 49% were unvaccinated before their first COVID-19 infection. The differences in terms of Post-COVID Condition were clear.
Among the vaccinated group, 0.4% were diagnosed with Post-COVID Condition by healthcare services during the follow-up period, up to and including November 2022. The corresponding proportion among the unvaccinated group was 1.4%.
Vaccination was associated with a 58% risk reduction of being diagnosed with Post-COVID Condition compared to unvaccinated individuals. This is after adjusting for age, gender, socioeconomics, current virus variant, other morbidity (diabetes, cardiovascular disease, respiratory disease, and psychiatric illness), and the number of healthcare contacts during 2019.
Protection increases with more doses
The link between vaccination and Post-COVID Condition was also found to be dose-dependent. With one dose received before contracting COVID-19, the risk of Post-COVID Condition was 21% lower than for unvaccinated individuals. The risk reduction was 59% with two doses, and 73% with three.
Protection against Post-COVID Condition was slightly stronger among 55- to 64-year-olds than other age groups, and among the group of men as a whole compared to women. Being newly vaccinated at the onset of COVID-19 was also an advantage; Protection was also slightly better if the time between last vaccination and infection was relatively short.
Those who contracted COVID-19 when the delta variant of the virus predominated had somewhat stronger protection. However, there were no clear differences between different vaccines. Several doses of the same vaccine, AstraZeneca, Pfizer or Moderna, gave fairly equal protection. With the combination AstraZeneca followed by Pfizer, protection against Post-COVID Condition was estimated to be slightly lower in the study.
It is already known that vaccination protects against severe COVID-19 infection. The researchers have also shown that a diagnosis of Post-COVID Condition is more common among those who have been hospitalized for COVID-19, compared to those who have not been hospitalized. However, the protection against Post-COVID Condition described in the current study is not fully explained by the protection against severe COVID-19.
The importance of following recommendations
The first author of the study is Lisa Lundberg-Morris, a doctoral student in biomedicine at the University of Gothenburg's Sahlgrenska Academy and a clinical pharmacologist at Sahlgrenska University Hospital. The research was carried out at School of Public Health and Community Medicine at the University of Gothenburg, the with Fredrik Nyberg, a Visiting Professor in Register Epidemiology, and Maria Bygdell, a researcher within internal medicine and clinical nutrition, having main responsibility for the study.
"The results support a strong link between vaccination against COVID-19 before first-time infection and a reduced risk of being diagnosed with Post-COVID Condition, with more doses providing better protection," says Maria.
The researchers emphasize the importance of high vaccination rates and following recommendations. Post-COVID Condition often involves prolonged symptoms, with combinations of fatigue, apathy, and difficulties with memory and concentration. However, there is no clearly defined diagnosis. Fredrik explains:
"Although the study does not include information about the patients' symptoms, they have clearly had such significant problems that they were considered to have this diagnosis in their contacts with healthcare professionals."
"Future studies should evaluate whether additional vaccinations provide a corresponding increase in protection over time against Post-COVID Condition as a complication of COVID-19 infection."
