COVID-19 symptoms and duration of direct antigen test positivity at a community testing and surveillance site, January 2021-2022

Importance Characterizing clinical symptoms and evolution of community-based SARS Co-V-2 infections can inform health practitioners and public health officials in a rapidly changing landscape of population immunity and viral variants. Objective To characterize COVID-19 symptoms during the Omicron period compared to pre-Delta and Delta variant periods and assess the duration of COVID-19 BinaxNOW rapid antigen test positivity during the Omicron variant surge. Design, Setting, and Participants This public health surveillance study was undertaken between January 2021-January 2022, at a walk-up community COVID-19 testing site in San Francisco, California. Testing with BinaxNOW rapid antigen tests was available regardless of age, vaccine status, or symptoms throughout. Main Outcomes and Measures We characterized the prevalence of specific symptoms for people with a positive BinaxNOW test during the Omicron period and compared it to the pre-Delta and Delta periods. During the Omicron period, we examined differences in symptoms by age and vaccine status. Among people returning for repeat testing during Omicron period, we estimated the proportion with a positive BinaxNOW antigen test between 4-14 days from symptom onset or since first positive test if asymptomatic. Results Of 63,277 persons tested, 18,301 (30%) reported symptoms and 4,568 (25%) tested positive for COVID-19. During the Omicron period, 41.6% (3032/7283) of symptomatic testers tested positive, and the proportion reporting cough (67.4%) and sore throat (43.4%) was higher than during Delta and pre-Delta periods. Congestion was higher during Omicron (38.8%) than during the pre-Delta period and loss of taste/smell (5.3%) and fever (30.4%) were less common. Fevers and myalgias were less common among persons who had received boosters compared to unvaccinated people or those who received the primary series. Five days after symptom onset, 31.1% of people with COVID-19 stated their symptoms were similar or worsening. An estimated 80.2% of symptomatic re-testers remained positive five days after symptom onset and 60.5% after ten days. Conclusions and Relevance COVID-19 upper respiratory tract symptoms were more commonly reported during the Omicron period compared to pre-Delta and Delta periods, with differences by vaccination status. Antigen test positivity remained high after 5 days, supporting guidelines requiring a negative test to shorten the isolation period. Question During the Omicron period, are there differences in COVID-19 symptomatology compared to the pre-Delta and Delta periods and how long do rapid antigen tests remain positive? Findings In this community-based surveillance study we detected differences in symptomatology between the Omicron period and prior variant-periods, and by age and vaccination status. Five days after symptom onset, 80% remained positive with a BinaxNOW test. Meaning During the Omicron period, differences in symptomatology may be due to rising population immunity and a new variant. BinaxNOW positivity remained high among re-testers, which supports guidelines that use rapid tests to shorten the isolation period. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This program was supported by the University of California San Francisco, John P. McGovern Foundation, and the Chan Zuckerberg Health Initiative. The BinaxNOW cards were provided by the California Department of Public Health. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was conducted under a public health surveillance program that was reviewed by the UCSF Committee on Human Research and determined to be exempt and waived from IRB oversight. All participants provided informed consent in their preferred language prior to survey administration and COVID-19 testing. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present work are contained in the manuscript