In a recent study posted to the Journal of General Internal Medicine researchers evaluated the effect of coronavirus disease 2019 (COVID-19) vaccines on the symptomatic prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections beyond the acute phase of the disease.
Genetic mutations in the viral spike (S) glycoprotein enhance the affinity of viral protein binding with the host angiotensin-converting enzyme 2 (hACE2) receptors. This causes evasion of protective host immune mechanisms along with an up-regulation of pro-inflammatory mediators such as cytokines, interleukins, and interferons. The viral immune escape facilitates unrestricted entry into host cells and enables constant intracellular viral replication.
The presence of residual positive-sense viral ribonucleic acid (RNA) in the host could interact with the negative-sense or intermediate replicative template RNA to synthesize new copies of viral RNA and increase viral titers. To this end, the presence of residual viral RNA could contribute to the persistence of symptoms in SARS-CoV-2 infections.
COVID-19 vaccines consist of attenuated virus or viral vectors, the administration of which leads to the generation of proteins unique to SARS-CoV-2 and immune responses to protect the host against COVID-19.
Although previous studies reported the prevalence of symptoms in post-acute COVID-19, data on the evolution and duration of symptoms, risk factors, and therapeutic measures are sparse. Although it is known that vaccination prevents the acquisition and development of acute complications in SARS-CoV-2 infections, the preventive and therapeutic effects of vaccines on the post-acute phase of long COVID-19 (LC) is uncertain.
About the study
In the present study, the researchers evaluated the association between vaccination status and the development of six basic post-acute COVID-19 symptoms: shortness of breath, loss of memory or concentration difficulties, headache, fatigue, and loss or alterations in taste and smell.
Data was obtained between 23 April and 27 July 2021 with the help of an online survey. The survey was filled by 6,987 Swiss residents with COVID-19 confirmed by reverse-transcriptase polymerase chain reaction (RT-PCR) at the outpatient department of University Hospitals of Geneva.
Information on the symptoms developed in these individuals beyond the acute phase of COVID-19 and the status of their vaccination were obtained using the survey.
Results and discussion
A total of 2,094 (29.9%) individuals responded to the survey, of which 1,596 symptomatic participants reported post-COVID-19 symptoms. Comorbidities, if any, were present before the onset of COVID-19 symptoms in these patients. This indicates the absence of confounding bias in the study.
Only 47.1% of the study population were vaccinated, of which 26.6% and 47.8% received single dose and double doses, respectively. After vaccination, COVID-19 symptoms vanished in 30.8% of the patients whereas 4.7% of cases showed improvement. Stable symptoms were observed in 28.7% and the symptoms worsened in 3.3% of patients. The evolution of symptoms was reported by 29% of patients whereas 2.6% of participants did not prefer to answer. The post-acute phase symptoms improved in 69.6% of cases and worsened in 82.3% of cases within five days of vaccination.
The researchers observed that single, as well as double-dose vaccinations, decreased the prevalence of all the six basic COVID-19 symptoms. The second vaccination dose led to a significant reduction in the prevalence of shortness of breath and taste alterations.
The researchers concluded that COVID-19 vaccines decrease the prevalence of cardinal symptoms present beyond the acute phase of SARS-CoV-2 infections, based on these survey-study findings. However, the presence of symptomatic individuals who chose to refrain from vaccination could give rise to identification bias, leading to the under-representation of the study samples and potentially affecting the study results.
Future studies including randomized controlled trials, systematic reviews, and meta-analyses must be carried out to assess the differences in post-COVID-19 symptomatic health among vaccinated and unvaccinated individuals. Future research must also be aimed at the evaluation of the comparative effect of single and double doses of different types of vaccines. The data obtained could be used to ascertain the type of vaccine that is most effective against COVID-19, the most effective vaccine dosage, and to motivate people to get vaccinated and reduce the global health burden of SARS-CoV-2 infections.