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).