Ongoing Symptoms After Acute SARS-CoV-2 or Influenza Infection in a Case-Ascertained Household Transmission Study: 7 US Sites, 2021–2023

Background The prevalence and risk factors for ongoing symptoms following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) [SCV2]) or influenza infection are not well characterized. We conducted a prospective cohort study of households wherein ≥1 individual was infected with SCV2 or influenza to evaluate prevalence of and factors associated with ongoing symptoms at 90 days. Methods Index cases and their household contacts provided baseline health and sociodemographic information and collected daily respiratory specimens for 10 days following enrollment. Participants completed a follow-up survey 90 days after enrollment to characterize ongoing symptoms. Results We analyzed 1967 participants enrolled between December 2021 and May 2023. The risk of ongoing symptoms did not differ by infection status in SCV2 (SCV2-positive: 15.6%; SCV2-negative: 13.9%; odds ratio [OR]: 1.14; 95% CI: .7–1.69) or influenza (influenza-positive: 8.8%; influenza-negative: 10.0%; OR: .87; 95% CI: .45–1.72) households. However, among study participants with a documented infection, SCV2-positive participants had nearly twice the odds of ongoing symptoms as influenza-positive participants (OR: 1.92; 95% CI: 1.27–2.97). Conclusions These results suggest that SCV2 households have a significantly higher prevalence of ongoing symptoms compared with influenza households (OR: 1.78; 95% CI: 1.28–2.47). Among participants with SCV2 infection, underlying conditions (adjusted OR [aOR]: 2.65; 95% CI: 1.80–3.90) and coronavirus disease 2019 (COVID-19)–like symptoms (aOR: 2.92; 95% CI: 1.15–7.43) during acute infection increased odds of ongoing symptoms at 90 days, whereas hybrid immunity reduced the odds of ongoing symptoms (aOR: 0.44; 95% CI: .22–.90).