Vaccination appeared to reduce the likelihood of continuing symptoms of long COVID, British researchers found.
Among adults who were first infected with the virus and then received a COVID-19 vaccine, one dose was linked to an initial 12.8% (95% CI -18.6 to -6.6, P<0.001) reduction in the odds of long COVID, and a second dose was linked to an initial 8.8% (95% CI -14.1 to -3.1, P=0.003) decline, reported Daniel Ayoubkhani, MSc, of the Office for National Statistics in Newport, Wales, and colleagues.
This was followed by a 0.8% decrease every week over the next 9 weeks, they wrote in The BMJ.
In February, the U.K. Health Security Agency released a review that showed that vaccinated people were less likely to experience long COVID symptoms, and that the vaccine may aid in recovery from these symptoms even if a person has already contracted the illness.
“Greater evidence is therefore needed on the symptomology of SARS-CoV-2 infection after vaccination, which may facilitate informed decision making among individuals with long COVID,” Ayoubkhani’s group wrote.
However, an accompanying editorial by Manoj Sivan, MD, of the University of Leeds in England, and colleagues suggested that research is still a long way from proving a causal relationship between vaccines and minimal damage from long COVID, and that the main reason for those previously infected to get vaccinated is to “reduce the risk of reinfection.”
“People with long COVID need timely investigation, management, and rehabilitation in specialist clinics, including identification of thrombotic phenomena, cardiac dysrhythmias, and dysautonomia,” Sivan’s group wrote, adding that “a clear explanation for how vaccines might reduce the multisystem manifestations of long COVID is still lacking.”
Ayoubkhani and colleagues examined data on 28,356 adults ages 18 to 69 who participated in the COVID-19 Infection Survey and who received at least one dose of adenovirus vector or mRNA vaccine after testing positive for SARS-CoV-2.
Participants’ mean age was 46, 56% were women, and 89% were white. Median follow-up was 141 days from the first vaccine dose and 67 days from the second dose. About a quarter of participants reported long COVID symptoms at least once during the follow-up period, the authors said. They noted that 84% of participants were “double vaccinated” by September 2021.
Approximately 17% of participants reported “limitation of activities” at least once during the follow-up period. One dose of vaccine was associated with an initial 12.3% decrease (95% CI -19.5 to -4.5, P=0.003) in the odds of activity-limiting long COVID, and a second dose was associated with an initial 9.1% decrease (95% CI -15.6 to -2.1, P=0.01), followed by a 0.5% decrease per week until the end of follow-up.
There was no significant difference in long COVID trajectories between those who received the mRNA vaccine and those who received the adenovirus vector vaccine, Ayoubkhani and team added.
Limitations to the study included its observational design, potential unmeasured confounders, and the fact that a change in symptoms following vaccination may simply have been due to the “relapsing and remitting symptoms” of long COVID versus “a causal effect of the vaccine,” they wrote.
The authors recommended further research to understand this in the context of the Omicron variant, as well as “the biological mechanisms underpinning any improvements in symptoms after vaccination, which may contribute to the development of therapeutics for long COVID.”
The COVID-19 Infection Survey was supported by the British government.
Ayoubkhani disclosed no conflicts of interest.
Co-authors disclosed support from the National Institute for Health Research (NIHR), the Huo Family Foundation, and the NIHR Oxford Biomedical Research Centre. One co-author disclosed being an NIHR senior investigator. One co-author disclosed a lived experience of long COVID and being a co-investigator on the NIHR-funded STIMULATE-ICP study.
Sivan and colleagues disclosed no conflicts of interest.