A study published in Antimicrobial Stewardship & Healthcare Epidemiology describes the effectiveness of coronavirus disease 2019 (COVID-19) vaccines in reducing long-COVID symptoms.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative pathogen of COVID-19, is a respiratory virus that primarily attacks pulmonary epithelial cells. Besides the respiratory tract, the virus infects several other organs, including the gastrointestinal tract, heart, liver, kidney, and brain.
Many SARS-CoV-2-infected patients persistently experience long-term symptoms for weeks to months after clinical recovery. This condition is termed as post-COVID conditions or long-COVID. The most common long-term consequences are cardiovascular, respiratory, and neuropsychiatric symptoms. It has been estimated that more than 200 million people are affected by long-COVID globally.
In this systematic review and meta-analysis, scientists have explored the effectiveness of COVID-19 vaccines against long-COVID symptoms.
Clinical trials and real-world studies conducted during the pandemic have indicated that most COVID-19 vaccines are highly effective against wild-type SARS-CoV-2 infection, severe COVID-19, hospitalization, and mortality.
The scientists searched various scientific study-reporting databases to identify studies that investigated COVID-19 vaccine effectiveness against long-COVID in people who had received at least one dose of mRNA-based (Pfizer and Moderna) or adenoviral vector-based (AstraZeneca and Janssen) vaccines. The search period was restricted from December 2019 to April 2022.
A total of 26 studies were initially screened, of which ten were included in the systematic review. All studies were non-randomized, including five prospective cohort studies, four retrospective cohort studies, and one case-control study. Of the ten reviewed studies, six were included in the quantitative meta-analysis. The effectiveness of Pfizer, Moderna, Janssen, and AstraZeneca vaccines was evaluated in 9, 7, 6, and 5 studies, respectively.
Ten studies included in the qualitative analysis (systematic review) evaluated the effectiveness of COVID-19 vaccines against long-COVID in a total of 1,600,830 individuals.
Of these studies, four included participants who received vaccination only after contracting COVID-19, three who received vaccination before contracting COVID-19, and two who received vaccination before and after contracting COVID-19.
Regarding the data quality of included studies, eight were considered good quality, one was fair quality, and one was poor quality.
Six studies included in the meta-analysis evaluated the vaccine effectiveness in a total of 251,123 individuals. The prevalence of long-COVID was estimated to be 39% among unvaccinated individuals and 37% among vaccinated individuals.
The most reported symptoms were fatigue, muscle weakness, muscle pain, anxiety, impaired memory, sleep disorders, and breathlessness. The average vaccine effectiveness against long-COVID was estimated to be 29% among individuals who received at least one dose of the COVID-19 vaccine. Specifically, the vaccine effectiveness was 35% among individuals who received vaccination before contracting COVID-19. In comparison, vaccine effectiveness of only 27% was estimated among individuals who received vaccination after contracting COVID-19.
The study indicates that despite low efficacy, COVID-19 vaccines effectively reduce long-COVID symptoms caused by circulating SARS-CoV-2 variants during the study period.
The study also indicates that vaccines are more effective when administered before infection. However, the vaccines provide some level of protection to individuals who were immunized post-infection.
Encouraged by the findings, the scientists said,
Our findings can reassure that individuals with prolonged COVID-19 symptoms who have not been vaccinated that they should do so."
They also mentioned that more observational studies are required to determine the effectiveness of other vaccine types, booster vaccination, and heterologous vaccination.