Covid-19 Vaccine Effectiveness Against Sars-Cov-2-Confirmed Hospitalization in Six Countries and Areas in the Who European Region: Results from the First Two Years of the European Severe Acute Respiratory Infection Vaccine Effectiveness (Eurosave) Network, 2022–2023

Abstract

Background: Understanding COVID-19 vaccine effectiveness (VE) in preventing severe disease is critical to inform vaccine policy. We used the test-negative design to estimate VE against SARS-CoV-2-confirmed hospitalisation in adults ≥ 18 years in the eastern WHO European region.

Methods: We included patients hospitalised for severe acute respiratory infection (SARI) at sentinel surveillance sites in Albania, Georgia, Kyrgyzstan, North Macedonia, Serbia, and in Kosovo.* We collected demographic information, COVID-19 vaccination history, and tested respiratory samples for SARS-CoV-2 by RT-PCR. We calculated VE of any vaccine dose received within 12 months (Annual VE) as [(1 – adjusted Odds Ratio) x 100%] using a one-stage pooled analysis. The reference group included unvaccinated individuals and those who received their last vaccine > 12 months before symptom onset.

Findings: During 1 January 1, 2022 – November 20, 2023, of 5165 patients, 57% were unvaccinated, 26% received a primary series vaccine (PS), and 15% at least one booster. Most PS vaccines and boosters were BNT162b2 (46% and 65%, respectively) and CoronaVac (23% and 18%). Overall 1009 (20%) patients were SARS-CoV-2-positive. VE was 60% (95% Confidence Interval (CI) 12–82) for last vaccine received 7–89 days before symptom onset, 59% (95% CI 31–76) for 90–179 days, 7% (95% CI -29–33) for 180–269 days, and -6% (95% CI -44-22) for 270–365 days.

Interpretation: During nearly two years of Omicron circulation in the eastern WHO European region, COVID-19 vaccination reduced the risk of hospitalisations by more than half for 6 months following vaccination.

Funding: This study was funded by the World Health Organization, Regional Office for Europe through a cooperative agreement with the U.S. Centers for Disease Control and Prevention.

Declaration of Interest: None of the authors on this manuscript have any competing interests or conflict of interests to declare.

Ethical Approval: The study was considered to be enhanced public health surveillance and therefore exempted by the local ethics review committee in Albania (The Scientific Ethical Council of the Institute for Public Health of Albania (#713), and WHO Research Ethics Review Committee (ERC) (# CERC.0098G); Georgia (Georgian National Center for Disease Control and Public Health Institutional Review Board # 2021-067 and WHO ERC # CERC.0098C), Kyrgyzstan (The Ethics Committee of the Scientific and Production Association “Preventive Medicine" of the Ministry of Health and Social Development of the Kyrgyz Republic # 01-4/190 and WHO ERC # CERC.0098A), and North Macedonia (Ethical Review Committee at the Medical Faculty of the University Ss Cyril and Methodius # 03-544012 and WHO ERC # CERC.0098E). The study was considered research and approved by the local ERC and the WHO ERC in Serbia (Ethics Committee of the Institute for Public Health of Serbia #6501/1 and WHO ERC #CERC.0098D); and Kosovo8 (Doctors Chamber Ethical Review Committee reference # 57/2021/1 and WHO ERC # CERC.0098B).

Keywords: COVID-19 vaccine, vaccine effectiveness, severe acute respiratory infection, Europe, Albania, Serbia, North Macedonia, Kyrgyzstan, Kosovo