New research from the National Institutes of Health casts doubt on the theory that rebounding COVID-19 symptoms are due to an impaired immune response.
The study, published Oct. 6 in Clinical Infectious Diseases, assessed blood samples and other clinical tests from eight adult COVID-19 patients with rebounding symptoms, six of whom took Paxlovid. Six patients who did not have rebounding symptoms were also included in the study as a control group.
Researchers found no evidence of genetic mutations that would suggest patients were infected with a virus strain resistant to Paxlovid. There was also no evidence of delayed antibody development in patients who took Paxlovid and had rebounding symptoms. In fact, T-cell responses were higher in patients with rebounding symptoms compared to those who did not see symptoms return.
"The findings suggest that rebound symptoms could be partially driven by the robust cellular immune response to residual viral RNA throughout the respiratory tract, rather than an impaired immune response allowing viral replication," the National Institutes of Health wrote in an Oct. 6 news release.
The study authors said more research is needed to fully understand the clinical importance and epidemiological consequences of rebounding COVID-19 symptoms.