Asymptomatic surveillance testing for COVID-19 in health care professional students: lessons learned from a low prevalence setting

During the study's time frame, the Kingston, Frontenac, Lennox & Addington (KFL&A) public health region reported 1,494 confirmed cases of COVID-19 (Fig. 2). The test positivity rate ranged between 0.0% to 2.01% (May 8th, 2021). 35.91% and 45.7% of cases were identified as B.1.1.7 (alpha) B.617.2 (delta), respectively. KFL&A was considered a low prevalence area for COVID-19 throughout the first, second and third wave. However, the highest prevalence of COVID-19 cases occurred in the 18- to 29-year-old age category (697 cases; 46.7%) in the highest population density area, including the downtown core in which many students live [15]. Between August 31st, 2020 to June 24th, 2021, Queen’s University reported a total of 317 COVID-19 infections within the student population. Off campus students accounted for 88% (n = 279) while students in residences accounted for 12% (n = 38). Overall, SARS-CoV-2 infections in the Queen’s University population accounted for 20.4% of the KFL&A’s public health region’s SARS-CoV-2 infections (n = 1557) during the same period [16].

Fig. 2figure 2

Kingston, Frontenac, Lennox & Addington COVID-19 case load between June 15th, 2020, to June 23rd, 2021. Generated from KFL&A public health data

The KFL&A public health team recorded two outbreaks in Queen’s University residences which met the definition of a congregate setting from March 11th, 2021 to April 1st, 2021 (n = 17) and April 24th, 2021 to May 18th, 2021 (n = 18) (data provided by KFL&A Public Health). The news media reported on 4 infections in September, 54 cases being associated with house parties in December 2020 and 36 cases in April 2021 within the Queen’s University student population [17,18,19]. A concern upon initiation of this study was this occupational groups interaction with patients in long term care and clinical settings increasing their risk for COVID-19. Outbreaks in term care facilities and retirement homes between October 2020 and June 2021 were limited to 10 outbreaks comprised of 13 cases total. Additionally, there were no outbreaks in KHSC hospitals or Providence Care throughout the duration of this study (data provided by KFL&A Public Health).

Several post-secondary institutions in the United States have published their COVID-19 measures and outcomes in allowing students to engage in in person learning. Indiana University with 12,000 students (8000 undergraduates 85% of whom live on campus) returned to in-person learning in August 2020. Within two weeks they experienced an outbreak of 371 cases mainly from students living off campus and pivoted to remote learning and 2-weeks of isolation before returning to in-person learning. Similar to our study, increased testing, tracing, and isolation measures allowed the University of Indiana to return to in-person learning [20]. The Public University Campus in Washington State enrolled 16, 476 individuals and performed 29, 783 SARS-CoV-2 test throughout fall 2020, they detected 236 infections representing 0.79% of their swabs. Seventy-five percent of positive cases reported at least 1 of the following: symptoms (60.8%), exposure (34.7%), or high-risk behaviour (21.5%) [21]. In comparison with our smaller health care professional student cohort we did not detect SARS-CoV-2 in the 1200 NP samples collected, this further demonstrated the utility of public health screening questionnaires as the aforementioned study reports that many symptoms and exposures were risk factors in testing positive.

Holiday breaks such as spring break warranted additional caution. Specifically, the Chicago Department of Public Health identified 158 cases among undergraduate students in the city’s university between March 15th, and May 3rd 2021, of infected students 63.6% reported recent travel outside Chicago for spring break and 40.7% reported indoor social exposure [22].

Some participants engaged in intra-provincial, national, and international travel throughout the study for personal or training-related purposes (i.e., residency placements in other cities), which may have increased their risks of contracting SARS-CoV-2 however the number of SARS-CoV-2 infections identified through questionnaires and serology testing in our study was too low to assess these risk factors.

Despite these potential increased risks to COVID-19 exposure, our study revealed that asymptomatic RT-PCR NP testing of a higher risk occupational group from a geographical location with a low COVID-19 prevalence rate revealed no detectable SARS-CoV-2 infection. Further, there were limited COVID-19 cases within the hospital during the study, meaning that the risk of a health care professional learner contracting COVID-19 from a patient was low. RT-PCR NP swabs are the gold standard for identifying COVID-19 infection; however, they are resource-intensive requiring physician supervision, clerical, nursing and technical staff. Moreover, this testing occurred at a time of extremely high demand on the laboratory services. Throughout the pandemic, it has been essential to allocate resources appropriately while adapting to variants of concern such as B.1.1.529 (omicron). As vaccines have become widely available in Canada, it is crucial to continually evaluate the use of non-pharmacological interventions such as RT-PCR, rapid antigen tests, symptom screening tools, contact tracing and masking to determine what interventions will keep health care professional learners’ and the community safe. Our data suggests that negligible asymptomatic infection occurred in this group during a time of mandatory masking, physical distancing and restrictions on gathering. While the negative results with the gold standard test were reassuring in the context of the events that were unfolding, NP- RT-PCR testing was very resource intense and this an important consideration for future decision making in this and future pandemics.

Limitations of this study include sampling bias, as health care professional students who participated in this study may have engaged in less risky behaviour than some of their peers that were not enrolled in this study. NP SARS-CoV-2 RT-PCR testing was mandatory for all medical students to engage with in-person learning requirements, but they did not have to participate in this study in order to obtain testing. RT-PCR NP testing was free and accessible to students through our research study and public health. Whereas the other Queen’s FHS’ programs did not require mandatory testing the asymptomatic infection of COVID-19 is not as thoroughly captured in these specific student populations.

Two other respiratory viruses, influenza A&B and HOPV, were also not identified. Infections with these viruses were at a historic low. This is likely due to the low rates of these viruses circulating in the general population as a result of increased public health safety measures such as increased hand-washing, physical distancing, mask use, decreased contacts and higher influenza vaccine coverage [23,24,25,26].

Future directions include evaluating the seropositivity of this group due to previous infection and vaccine-induced immunity, and mental health outcomes.

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