Risk of COVID-19 infection among frontline healthcare workers during the COVID-19 pandemic.

BACKGROUND

In the initial stages of the coronavirus disease 2019 (COVID-19) pandemic, healthcare workers (HCWs) who were immunologically naive to COVID-19, were exposed to a highly transmissible virus.

AIM

To compare infection risk among HCWs in high-risk (HR) and low-risk (LR) areas.

METHODS

Data on reverse transcriptase-polymerase chain reaction confirmed clinical infection and samples for nucleocapsid, and spike protein antibodies were collected at five time-points (T1 to T5) from HCWs in the emergency department and intensive care unit (HR group) and pre-clinical and para-clinical areas (LR). For the sero-study, only participants who provided at least one baseline sample and one during the second wave (T4 or T5) were analysed. Since Covishield elicits only spike protein antibodies, subclinical infection was diagnosed if asymptomatic unvaccinated and Covishield vaccinated individuals tested positive for nucleocapsid antibody.

RESULTS

Overall, by T5, clinical infection rate was similar in the HR (120/366, 32.8%) and LR (22/82, 26.8%) groups ( = 0.17). However, before vaccination (T3), more HCWs in the HR group developed COVID-19 infection (21.9% 8.8%, = 0.046). In the sero-study group, clinical infection occurred in 31.5% (45/143) and 23.7% (14/59) in the HR and LR groups respectively ( = 0.23). Spike antibody was detected in 140/143 (97.9%) and 56/59 (94.9%) and nucleocapsid antibody was positive in 95/143 (66.4%) and 35/59 (59.3%) in the HR and LR groups respectively ( = 0.34). Subclinical infection rate (HR 34.9%, LR 35.6%, = 0.37) and hospitalization rate were similar. There was no mortality.

CONCLUSION

Before vaccination, HCWs in HR areas had a higher risk of infection. Seroprevalence studies suggest that sub-clinical infection was not uncommon.