COVID-19 survivors have a significantly higher rate of ongoing symptoms than those who had influenza, a University of North Carolina–led research team reports, identifying underlying medical conditions and symptomatic infection as risk factors and hybrid immunity (vaccination plus previous infection) as protective.
Most participants had some COVID immunity
For the study, published yesterday in Clinical Infectious Diseases, the researchers conducted a prospective cohort study of households in which at least one member had COVID-19 or flu to evaluate the prevalence of and factors for ongoing symptoms at 90 days.
The research took place at seven US sites via the Respiratory Virus Transmission Network from December 2021 to May 2023. The study period spanned the predominance of the Delta and Omicron SARS-CoV-2 variants.
The previously infected patients and their infected or uninfected household members provided baseline health and sociodemographic information, dried-blood samples, and respiratory specimens every day for 10 days. They also completed a follow-up symptom survey 90 days later. Most had experienced mild infections.
Of the 1,967 participants, 74.3% were from COVID-19 households, 26.6% were from flu households,42.6% were male, and 64.7% were adults. Most participants had some COVID-19 immunity (vaccine only, 45.9%; previous infection only, 11.3%; hybrid, 28.3%), and 57.8% had received that season's flu vaccine.
Fatigue, sleep problems, congestion
A total of 13.6% of participants reported at least one symptom at 90 days. Among those in COVID-19 households, 15.6% of COVID-positive participants and 13.9% of COVID-negative participants reported symptoms at 90 days, compared with 8.8% of flu patients and 10.0% of flu-negative participants.
The results of this analysis are notable for the potential protection from hybrid immunity, which could suggest a reduced incidence of ongoing symptoms going forward.
The risk of lingering symptoms didn't differ by infection status for COVID-19 (COVID-positive, 15.6%; COVID-negative, 13.9%; odds ratio [OR], 1.14) or flu (flu-positive, 8.8%; flu-negative, 10.0%; OR, 0.87). But among participants who had a documented infection, those who had COVID-19 were at nearly twice the risk for continuing symptoms compared with those with flu (OR, 1.92).
The findings suggest that COVID-19 households have a significantly higher rate of ongoing symptoms than those with flu (OR, 1.78), the study authors said. COVID-19 survivors who had chronic conditions (adjusted OR [aOR], 2.65) and COVID symptoms during infection (aOR, 2.92) were more likely to have symptoms at 90 days, whereas hybrid immunity was protective (aOR, 0.44).
The most common COVID-19 symptoms in adults who at least one symptom at 90 days were fatigue, sleep problems, and congestion. The proportion of specific ongoing symptoms in flu households wasn't assessed because of the small sample size.
"The results of this analysis are notable for the potential protection from hybrid immunity, which could suggest a reduced incidence of ongoing symptoms going forward," the study authors wrote. "These results, combined with the small sample sizes, highlight the continued need for monitoring to understand ongoing symptoms and what factors may impact prevalence."
