# COVID-19 vaccine effectiveness among healthcare workers during the Omicron period in the country of Georgia, January – June 2022

## TL;DR

This study measured how effective a first booster dose of the COVID-19 vaccine was for healthcare workers in Georgia during the Omicron wave in 2022.

## Contribution

The study provides new insights into the short-lived effectiveness of a first booster dose against Omicron in healthcare workers.

## Key findings

- The first booster dose showed 40% effectiveness in the first 30 days but protection declined rapidly.
- Relative to the primary vaccine series, the booster was 58% more effective initially but this dropped to -9% after 60 days.
- Vaccine effectiveness waned quickly, highlighting the need for timely vaccination before high-risk periods.

## Abstract

Understanding COVID-19 vaccine effectiveness (VE) in healthcare workers (HCWs) is critical to inform vaccination policies. We measured COVID-19 VE against laboratory-confirmed symptomatic infection in HCWs in the country of Georgia from January – June 2022, during a period of Omicron circulation.

We conducted a cohort study of HCWs in six hospitals in Georgia. HCWs were enrolled in early 2021. Participants completed weekly symptom questionnaires. Symptomatic HCWs were tested by RT-PCR and/or rapid antigen test (RAT). Participants were also routinely tested, at varying frequencies during the study period, for SARS-CoV-2 by RT-PCR or RAT, regardless of symptoms. Serology was collected quarterly throughout the study and tested by electrochemiluminescence immunoassay for SARS-CoV-2 antibodies. We estimated absolute and relative VE of a first booster dose compared to a primary vaccine series as (1-hazard ratio)*100 using Cox proportional hazards models.

Among 1253 HCWs, 141 (11%) received a primary vaccine series (PVS) and a first booster, 855 (68%) received PVS only, and 248 (20%) were unvaccinated. Most boosters were BNT162b2 (Comirnaty original monovalent) vaccine (90%) and BBIBP-CorV vaccine (Sinopharm) (9%). Most PVS were BNT162b2 vaccine (68%) and BBIBP-CorV vaccine (24%). Absolute VE for a first booster was 40% (95% Confidence Interval (CI) -56–77) at 7–29 days following vaccination, -9% (95% CI -104–42) at 30–59 days following vaccination, and -46% (95% CI -156–17) at ≥ 60 days following vaccination. Relative VE of first booster dose compared to PVS was 58% (95% CI 1–82) at 7–29 days following vaccination, 21% (95% CI -33–54) at 30–59 days following vaccination, and -9% (95% CI -82–34) at ≥ 60 days following vaccination.

In Georgia, first booster dose VE against symptomatic SARS-CoV-2 infection among HCWs was moderately effective but waned very quickly during Omicron. Increased efforts to vaccinate priority groups in Georgia, such as healthcare workers, prior to periods of anticipated high COVID-19 incidence are essential.