1395. COVID 19 Incidence rates were not different among high risk health-care workers and non-health workers after SARS-CoV-2 vaccination: a prospective study in Cali-Colombia.

Abstract Background The seroprevalence of COVID-19 among health-care workers (HCWs) is still not well characterized in Latin America and the Caribbean. The objective of this study was to compare incidence rates (IR) during the COVID-19 pandemic among HCWs vs. non-HCWs in a university hospital in Cali, Colombia. Figure 1Figure 2 Methods A prospective study was performed. The study included two groups: HCWs with high-risk contact of SARS-CoV-2 infections vs. administrative hospital workers (non-HCW). Seroprevalence of SARS-CoV-2 antibodies between both groups was compared according to vaccination history and confirmed SARS-CoV-2 infection during follow-up (March 6th, 2020, to February 28th, 2022). The study was developed in three phases according to the infection waves in Colombia, measuring antibodies anti-nucleocapsid and anti-spike serum concentration in each one. A descriptive analysis was done to compare both groups and IR per month (Figure 1). Results 480 participants were included, 291 (60.6%) were HCWs, and 189 (39.4%) were non-HCWs. After the second wave and before vaccination, the accumulative seroprevalence was 40.6%: 49.1% of HCWs vs. 27.5% of non-HCWs (p< 0.001). 9.2% of HCWs and 7.9% of non-HCWs seropositive individuals had an asymptomatic infection (p=0.447). Of the 51.9% of susceptible HCWs and 72.5% of susceptible non-HCWs before the third wave, the risk of developing SARS-CoV-2 infection was 9.2% and 12.8%, respectively. After 24 months, the infection rate was higher in HCWs and non-HCWs (55.6% vs. 41.9%, p< 0.001) (Figure 2). The total IR was 31.4/1,000 person-month, with an IR difference of 21/1,000 person-month being higher in HCWs comparing non-HCWs (40.7 vs. 19.8, p< 0.001), but after vaccination (April 2021), the IR difference was not significative (IR difference 5%, p=0.1605). The asymptomatic disease was 9.8% of HCWs vs. 10.2% of non-HCWs. Since vaccination, 93.6% of workers had positive anti-S antibodies after 2 doses; and 100% had them after 3rd dose. SARS-CoV-2 Omicron variant increased cases during the fourth wave, more in non-HCWs. Conclusion Before vaccination, HCWs had higher infection rates, mainly after the second wave. However, after the immunization, the IR in both groups significantly decreased and equalized in both groups. Disclosures All Authors: No reported disclosures.