Ongoing symptoms and functional impairment 12 weeks after testing positive to SARS-CoV-2 or influenza in Australia: an observational cohort study

Objective In a highly vaccinated Australian population we aimed to compare ongoing symptoms and functional impairment 12 weeks after PCR-confirmed COVID-19 infection with PCR-confirmed influenza infection. Methods and Analysis The study commenced upon a positive PCR test for either COVID-19 or influenza in June 2022 during concurrent waves of both viruses. Participants were followed up 12 weeks later in September 2022 and self-reported ongoing symptoms and functional impairment. We conducted a multivariate logistic regression analysis, controlling for age, sex, First Nations status, vaccination status, and socio-economic profile. Results There were 2 195 and 951 participants in the COVID-19 and influenza-positive cohorts respectively. After controlling for potential predictor variables, we found no evidence to suggest adults with COVID-19 were more likely to have ongoing symptoms (21.4% vs 23.0%, aOR 1.18; 95% CI 0.92-1.50) or moderate to severe functional impairment (4.1% vs 4.4%, OR 0.81; 95% CI 0.55-1.20) at 12 weeks after their diagnosis than adults who had influenza. Conclusions In a highly vaccinated population exposed to the SARS-CoV-2 omicron variant, long COVID may manifest as a post-viral syndrome of no greater severity than seasonal influenza but differing in terms of the volume of people affected and the potential impact on health systems. This study underscores the importance of long COVID research featuring an appropriate comparator group.