Prospective Respiratory Outcomes from Tracking and Evaluating Community-based TeSting (Project PROTECTS): a community-based, prospective study of acute respiratory infections among adults across the USA - cohort profile.

purposeThe Prospective Respiratory Outcomes from Tracking and Evaluating Community-based TeSting study is a 2-year community-based, prospective cohort launched in 2024. The overall aim of the study is to better understand the burden and impact of acute and postacute COVID-19, influenza and respiratory syncytial virus (RSV) infections across the USA. Our key objectives are to measure the incidence and symptom burden of major respiratory viruses using home testing, measure incidence and risk factors for postacute symptoms of major respiratory viruses and investigate the impact of antivirals and vaccinations on acute and postacute symptoms of respiratory viruses.

participantsEnrolment began in June 2024 using internet-based strategies. Eligible participants were adults aged ≥18 years who were US residents, English language proficient and had no known SARS-CoV-2, RSV or influenza infections in the 3 months before screening. We prioritised enrolment of individuals who were at high risk for severe SARS-CoV-2 outcomes. After enrolment, participants were prompted to report the presence or absence of respiratory symptoms weekly. When respiratory symptoms occurred, participants completed serial at-home multipathogen rapid antigen tests for SARS-CoV-2, RSV, influenza A and influenza B viruses, and daily symptom reporting, including timing and severity. A subset of participants provided self-collected nasopharyngeal and saliva samples for PCR testing. Following a positive test and acute symptom reporting for up to 29 days, participants were followed monthly for 6 months to capture postacute symptoms. FINDINGS TO DATE: As of March 2025, 6206 people were enrolled in the cohort. The majority of the participants were over 50 years of age (61.4%), women (66.8%) and non-Hispanic white (75.2%), with a notable proportion having a college or postgraduate degree (68.4%) and an annual household income of >US$100 000 (40.7%). All 50 US states, the District of Columbia and Puerto Rico were represented in the cohort. Half of participants (51.8%) had received a COVID-19 vaccine in the year prior to enrolment, and 19.5% who had reported at least one SARS-CoV-2 infection had a history of antiviral use. A majority of the cohort (95.6%) had at least one underlying medical condition or risk factor for severe COVID-19. Nine-month retention (93.7%) and adherence to the study protocol among participants was high. As of 18 April 2025, 4537/6206 (73.1%) participants had reported respiratory symptoms within 10 days of onset, with a median time to report of 2 days after onset, and 3814/4537 (84.1%) conducting at least one valid rapid test. Of these 3814 participants, 489 (12.8%) had tested positive for SARS-CoV-2, 324 (8.5%) for influenza A, 22 (0.6%) for influenza B and 113 (2.9%) for RSV by study rapid or PCR tests. FUTURE PLANS: We enrolled a large, diverse cohort with a high proportion at risk for severe COVID-19. We have collected over 3000 person-years of data on symptoms, outcomes and risk factors for three major respiratory infections, with high participant retention and engagement through 9 months of data collection. Research priorities include characterising acute and postacute symptoms of major respiratory illnesses and assessing the impact of antivirals and vaccination on the development of severe symptoms.