ABSTRACT
Background. Screening large groups of individuals entering a congregate setting has been a challenge during the COVID-19 pandemic. Current Infectious Disease Society of America guidelines recommend polymerase chain reaction (PCR)-based screening in symptomatic and at-risk individuals over antigen based testing due to higher sensitivity. However, there are limited real-world data describing secondary COVID-19 cases after different arrival testing strategies. Methods. Between January 1 - August 31, 2021 all trainees attending United States Air Force Basic Military Training underwent arrival testing for COVID-19. Trainees who arrived January 1, 2021 - May 21, 2021 were tested via PCR and those from May 24, 2021 - August 31, 2021 via antigen test. All trained in groups of 30-50 and slept in communal quarters. Symptomatic secondary cases within the first two weeks of training were identified by individual as well as training group and compared based on method of arrival testing. For this study, a case cluster was defined as > 5 cases. Results. A total of 24,601 trainees arrived during the study period with 406 (1.6%) trainees testing positive on arrival, of which 134 (33%) were symptomatic. Initial positivity rate was greater for PCR testing as compared to antigen testing (2.5% vs 0.4%, RR: 5.4, 95% CI: 4.0-7.3, p< 0.001). With PCR testing, training groups were significantly more likely to have a positive case on arrival (57% vs 11%, RR: 5.3, 95% CI: 3.7-7.7, p< 0.001). However, PCR testing was not associated with a difference in training groups with a secondary case (20% vs 22%, RR: 0.9, 95% CI: 0.66-1.2, p=0.53), number of training groups with a case cluster (4% vs 6.7%, RR: 0.61, 95% CI: 0.3-1.2, p=0.16), or number of days after arrival until development of symptomatic secondary case (median 8 vs 6.5 days, p=0.37) as compared to antigen testing. Conclusion. This study describes two strategies of arrival testing for COVID-19 in a congregate setting at high risk for disease transmission. In this study, PCR-based testing was associated with more arrival cases. However, there was no difference in the number of training groups having a secondary case or a case cluster. This study supports the utility of antigen-based arrival testing for congregate settings.
ABSTRACT
Background. Symptomatic COVID-19 screening has been a cornerstone of case identification during the pandemic. Despite the myriad of COVID-19 symptoms, screens have focused on fever, cough, and dyspnea. It is unknown how well these symptoms identify cases in a healthy military population. This study aims to evaluate the utility of symptom-based screening in identifying COVID-19 through different COVID-19 waves. Methods. A convenience sample of 600 active-duty service members who arrived at JBSA in 2021 and 2022 was included in this study. We compared 200 symptomatic service members who tested positive for COVID-19 in each of FEB-APR 2021 (prior to the emergence of the Delta variant), JUN-AUG 2021 (Delta variant was predominant), and JAN 2022 (Omicron variant was predominant). Collected data included test date, reported symptoms, and vaccination status. Comparisons were conducted via Chi-Square or Fisher's Exact test. Results. Of the 600 symptomatic active-duty service members who tested positive for COVID-19, the most common symptoms were sore throat (n=385, 64%), headache (n=334, 56%), and cough (n=314, 52%). While sore throat was the most prominent symptom during Delta (n=140, 70%) and Omicron (n=153, 77%), headache was the most common prior to Delta (n=93, 47%). There were significant differences in symptoms by vaccination status (Table 2). Overall, screening for fever, cough, and dyspnea had a 65.1% sensitivity in this cohort (Table 3) with its lowest sensitivity in the pre-Delta cohort (53.5%) and highest sensitivity in the fully vaccinated Omicron cohort (78.3%). Conclusion. In this descriptive cross-sectional study evaluating symptomatic military members with COVID-19, symptom prevalence varied based on the predominant COVID-19 variant as well as patients' vaccination status. As screening strategies evolve with the pandemic, changing symptom prevalence should be considered.
ABSTRACT
Background: The COVID-19 pandemic has been associated with significant spread in congregate settings and various forms of non-pharmaceutical interventions (NPI) have been implemented to prevent spread. Basic Military Training at Joint Base-San Antonio is the entrance to the US Air Force and has been associated with respiratory outbreaks in the past. A two-week arrival quarantine was implemented in March 2020. Effects on subsequent testing for COVID-19 after an arrival quarantine is unknown. Methods: The first four weekly cohorts of trainees who underwent an arrival quarantine between March 16-April 13 were monitored during their 7 week training for COVID-19 symptoms. Symptoms, medical testing, and days removed from training were collected on every patient with possible COVID-19 symptoms including cough, shortness of breath, or fever. Testing during the two-week arrival quarantine were compared to the subsequent five weeks of training. Nominal variables were compared by chi squared or Fisher's exact test as appropriate. Continuous variables were compared by Mann-Whitney U Test. Results: A total of 2,573 started training during study period, 89 (3.4%) had symptoms concerning for COVID-19 and were tested. 5 (6%) patients tested positive, all of whom in the arrival quarantine. Compared to patients who completed quarantine (n=29), patients in the arrival quarantine who tested negative for COVID-19 (n=54) were tested more often (26 trainees a week vs. 5.8 later in training, p=< 0.0001), and received more rapid flu tests (74% vs. 38%, p=0.001) and multiplex respiratory PCR (15% vs. 0%, p=0.05). Trainees in quarantine were isolated longer for symptoms than patients who completed quarantine (median 3 vs. 2, p=0.01). There was no difference in presenting symptoms for trainees in quarantine or after quarantine. Conclusion: Arrival quarantine appears to be an effective NPI, which in conjunction with other interventions prevented any COVID-19 transmission after quarantine completion. For those who went through arrival quarantine, there was more intense initial testing and initial longer symptomatic patient isolation, this was balanced by fewer symptomatic patients, less testing, and shorter isolations later in training.