Vaccination against COVID-19 appears to provide a small but significant protection against the development of post-COVID-19 condition
Patients who have a COVID-19 vaccination reduce their risk of subsequently developing post-COVID-19 condition (or long covid) although the effectiveness of the vaccine is low according to the findings of a meta-analysis by US researchers.
Vaccine effectiveness is a measure of how well vaccination protects individuals against a condition but differs from the efficacy measured in a trial, because efficacy cannot predict exactly just how effective a vaccine might be in a larger and more variable population. Nevertheless, real-world evidence suggests that some vaccines, such as BNT162b2, have an effectiveness comparable to that reported in phase III clinical trials. Although in practice, many patients make a full recovery after an acute COVID-19 infection, for a minority, there is the continuation or development of other symptoms. The World Health Organisation has described this as ‘Post COVID-19 condition’ and which occurs in individuals with a history of probable or confirmed COVID-19 infection, usually 3 months from the onset of COVID-19 with symptoms that last for at least 2 months and cannot be explained by an alternative diagnosis.
While the effectiveness of vaccination against COVID-19 is widely accepted, what is uncertain, is whether vaccination reduces the risk of post–COVID-19 condition. This was the subject of the current study by the US researchers who reviewed the literature on the effectiveness of COVID-19 vaccines for post–COVID-19 condition and pooled the results of published studies to allow for a more precise estimate of effectiveness. The team looked for studies that: involved vaccinated and unvaccinated individuals and evaluated the long-term effectiveness of the COVID-19 vaccine. Post–COVID-19 conditions were defined as a wide range of health symptoms that were present 3 or more weeks after having COVID-19. Any studies without a comparison between vaccinated and unvaccinated individuals (or other vaccinated control group) were excluded. The team calculated the pooled diagnostic odds ratio (DORs) for post–COVID-19 conditions between vaccinated (i.e., those who received at least 1 dose of a COVID-19 vaccine) and unvaccinated individuals.
Vaccination and effectiveness against post-COVID-19 condition
A total of 10 studies with 1,600,830 individuals evaluated the effect of vaccination on post–COVID-19 conditions and of which 6, were included in the meta-analysis. The pooled prevalence of post–COVID-19 conditions was 39.1% among those who were unvaccinated and 37.6% among those who received at least 1 dose.
The pooled DOR for post–COVID-19 conditions among individuals who received at least 1 dose was 0.708 (95% CI 0.69 – 0.73), giving an estimated vaccine effectiveness of 29.2% (95% CI, 27.5%–30.8%).
However, vaccine effectiveness varied depending on whether an individual received the vaccine before or after being infected with COVID-19. For example, effectiveness was 35.3% (95% CI 32.3% – 38.1%) among those who received the COVID-19 vaccine before having COVID-19 but 27.4% (95% CI 25.4% – 29.3%) among those who received it after being infected.
The authors concluded that COVID-19 vaccination before and after having COVID-19 provided a low but statistically significant decrease in post–COVID-19 conditions for the variants circulating during the study period. They added that a more standardised definition of post–COVID-19 conditions was also needed both for research and clinical purposes.
Marra AR et al. The effectiveness of coronavirus disease 2019 (COVID-19) vaccine in the prevention of post–COVID-19 conditions: A systematic literature review and meta-analysis. Antimicrob Steward Health Epidemiol 2022