Study finds no strong evidence to suggest vaccination improves symptoms of post-acute COVID-19 syndrome

The coronavirus virus 2019 (COVID-19) pandemic has been caused by the rapid outbreak of severe acute respiratory coronavirus syndrome 2 (SARS-CoV-2). It is now well-documented that symptoms of COVID-19 could persist beyond the acute phase of infection. The World Health Organisation (WHO) recently defined this condition as ‘long COVID’ or ‘post-acute COVID-19 syndrome’ (PACS). Symptoms of PACS may improve following SARS-CoV-2 vaccination, but there is limited data to study the underlying biological mechanism.

Study: The Effect of SARS-CoV-2 Vaccination on Post-Acute COVID-19 Syndrome (PACS): A Prospective Cohort Study. Image Credit: Starocean/Shutterstock

A new study available on Preprints with The Lancet* assessed the effect of SARS-CoV-2 vaccination on the symptomatology of individuals with PACS. Researchers also compared antibody dynamics between those with and without PACS.

Background

Some anecdotal reports from high-income countries suggest mitigation of PACS symptoms upon vaccination. An online survey among 900 PACS patients in the UK found that about 58% of respondents showed improvement of symptoms post-vaccination. These findings had certain limitations, including the presence of selection bias and the absence of a control group. However, the usefulness of vaccines in mitigating PACS has gained traction due to the urgent need for treatment for such patients.

Clinical data and immunological findings are jointly important to study the possible biological mechanism by which vaccination could improve PACS symptoms. Studying the difference in antibody dynamics among patients with PACS and those without could help shed further light on this issue. There is no study available that addresses this question.

A new study

RECoVERED is a prospective cohort study of adult patients experiencing mild to critical COVID-19 disease. Among the sample of PACS patients, vaccinated and unvaccinated participants were matched 1:1 based on certain parameters, such as age, sex, obesity status, and time since illness onset. Between matched pairs, scientists compared the average numbers of symptoms over time. They used exact logistic regressions to recover the proportion fully recovered within three months. The association between PACS status and the rate of decay of spike- and RBD-binding IgG titers up to 9 months after illness onset was also studied. 

Key findings

Researchers found no clear evidence of a beneficial effect of vaccination in terms of improving PACS symptoms. Serological data were used to verify these findings. No difference was observed with regard to the early neutralizing antibody titers between participants with and without PACS at three months after the onset of illness. The difference was also absent in antibody decay up to 9 months after illness onset.

Evidence of full recovery of PACS symptoms following SARS-CoV-2 vaccination is conflicting. Researchers of the current study documented that vaccination did not affect the odds of full recovery from PACS within three months from vaccination. The caveat is that the matched sample size was small; however, the findings suggest that the differential effect is unlikely to be substantial.

Inconclusive evidence has been presented in other studies, highlighting the importance of prospective population-based cohorts following COVID-19 patients at all levels of disease severity from illness onset onwards. Scientists, however, stressed that vaccination remains one of the most important interventions to avert both short- and long-term COVID-19 morbidity.

Overall, researchers did not observe any correlation between early virus binding and neutralizing antibody titers and the development of PACS. Among mild COVID-19 patients, those who developed PACS exhibited higher early RBD-binding antibody titers. The neutralizing IgG levels were seen to remain constant between PACS and non-PACS participants suffering from mild COVID-19 disease.

Limitations

In the current study sample, vaccination was not randomly assigned, and therefore confounding factors may be biasing results. Further, a significant proportion of the cohort was vaccinated around 12 months after the illness commenced, after which symptom questionnaires were no longer completed, thereby reducing the sample for matching. The participants also varied in their follow-up time, leading to measurement bias. Lastly, scientists also stated that the results are not generalizable to individuals infected with SARS-CoV-2 variants, other than the wild type.

Conclusion

In this study, researchers found no evidence of a strong effect of SARS-CoV-2 vaccination on the symptoms associated with PACS over time. They also did not find a significant effect of vaccination on time to full recovery from PACS following the first vaccination. Future research should focus on understanding the underlying biological mechanism of PACS as that will be highly effective to inform effective preventative measures and treatment options.

*Important notice

Preprints with The Lancet publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.