The Dynamic Risk of COVID-19-Related Events in Vaccinated Healthcare Workers (HCWs) from a Tertiary Hospital in Bucharest, Romania: A Study Based on Active Surveillance Data

Abstract

Our study describes the frequency and severity of COVID-19 in HCWs and estimates the dynamic risk of COVID-19-related events. We actively surveyed all HCWs from a tertiary infectious disease hospital from 26 February 2020 to 31 May 2023. Of 1220 HCWs, 62.9% (767) had at least one COVID-19 episode. The under 29 years (p = 0.0001) and 40-49 years (p = 0.01) age groups, nurses (p = 0.0001), and high-risk departments (p = 0.037) were characteristics significantly more frequent in HCWs with COVID-19 history. A higher percentage of boosters (53.2%; p < 0.0001) were registered in the uninfected group. The second episode of COVID-19 was significantly milder than the first. Data regarding clinical outcomes from 31 January 2021 to 31 May 2023 were analyzed in a follow-up study to determine the risk of COVID-19-related events. The Cox regression analysis revealed that HCWs with booster shots had a lower risk of COVID-19 across all events, symptomatic events, and moderate to severe events as adjusted hazard ratio (aHR) were: 0.71 (95%CI: 0.54-0.96), 0.23 (95%CI: 0.12-0.46), and 0.17 (95%CI: 0.07-0.43), respectively. Within the vaccinated subgroup, the HCWs with hybrid immunity and booster had aHR for all followed-up events of 0.42 (95%CI: 0.30-0.58), for symptomatic events of 0.52 (95%CI: 0.36-0.74), and 0.15 (95%CI: 0.03-0.66) for moderate to severe events. The risk of COVID-19 clinical events was lower for HCWs with at least one booster than those completely vaccinated.

Keywords: COVID-19; clinical outcome; healthcare workers; vaccines protection.

Figure 1

The workflow diagram for the active surveillance of HCWs in the National Institute for Infectious Diseases “Professor Dr. Matei Balș”, Bucharest, Romania, February 2020–May 2023.

Figure 2

Survival curves related to COVID-19 events in HCWs followed up from 31 January 2021 to 31 May 2023, INBI ”Prof. Dr. Matei Balș”, Bucharest. (A) Survival curves of moderate to severe events in completely vaccinated (n = 600), vaccinated and booster (n = 498), and nonvaccinated HCWs (n = 122). (B) Kaplan–Meier survival curves related to all COVID-19 events in complete vaccinated (n = 405), vaccinated and boosters (n = 378), hybrid immunity (n = 195), hybrid immunity and booster (n = 120). (C) Kaplan–Meier survival curves related to symptomatic COVID-19 events in vaccinated HCWs. (D) Kaplan–Meier survival curves related to moderate to severe events in vaccinated HCWs. Log-rank test was used for comparison of equality of survival curves of vaccinated groups: complete vaccination, vaccinated and booster, hybrid immunity, hybrid immunity, and booster.