OBJECTIVE: We hypothesized healthcare workers (HCW) with high-risk exposures outside the healthcare system would have less asymptomatic coronavirus 2019 (COVID-19) disease and more symptoms than those without such exposures .
DESIGN: A longitudinal point prevalence study during August 17- September 4 2020 and December 2nd - 23rd .
SETTING: Community based teaching health system .
PARTICIPANTS: All HCS were invited to participate . Among HCW who acquired COVID-19, logistic regression models were used to evaluate the adjusted odds of asymptomatic disease using high-risk exposure outside the healthcare system as the explanatory variable . The number of symptoms between exposure groups was evaluated with the Wilcoxon rank-sum test . The risk of seropositivity among all HCS by work exposure was evaluated during both periods .
INTERVENTIONS: Survey and serological testing . RESULT: Seroprevalence increased from 1.9% (95% CI 1.2% - 2.6 %) to 13.7% (95% CI 11.9% - 15.5 %) during the study . Only during Period 2 did HCW with the highest work exposure (versus low exposure) have an increased risk of seropositivity (RD 7% [95% CI 1% -13 %] ). Participants who had a high-risk exposure outside of work (compared to those without) had a decreased probability of asymptomatic disease (OR 0.38 [95% CI 0.16 - 0.86] ) and demonstrated more symptoms (median of 3 [IQR 5] vs 1 [IQR 2]; P = 0.001).
CONCLUSIONS: Health care acquired COVID-19 increases the probability of asymptomatic or mild COVID-19 disease compared to community acquired disease . This suggests infection prevention strategies (including masks and eye protection) may be mitigating inoculum and supports the variolation theory in COVID-19.