The impact of the COVID-19 vaccination programme on symptomatic and severe SARS-CoV-2 infection during a period of Omicron variant dominance in Ireland: December 2021-March 2023

Published: October 9, 2023

The Health Protection Surveillance Centre (HPSC) conducted a COVID-19 vaccine impact study from December 2021 to March 2023. An adapted formula from an internationally recognised and peer-review methodology was used to estimate COVID-19 vaccine impact in Ireland during the Omicron period. ^1,2 This study is currently unpublished pending publication in a peer-reviewed journal.

National surveillance data on notified outcomes, national vaccine coverage data, and vaccine effectiveness estimates sourced from the World Health Organization’s live systematic review of vaccine effectiveness,³ were used to estimate impact of the vaccination programme.

Between December 2021 and March 2023, the study estimated that the COVID-19 vaccination programme in Ireland prevented the following outcomes:

• 102,000 hospitalisations with COVID-19 – 81% of hospitalisations expected in the absence of vaccination.
• 3,300 ICU admissions due to COVID-19 – 89% of ICU admissions expected in the absence of vaccination.
• 16,000 deaths due to COVID-19 – 87% of deaths expected in the absence of vaccination.

The study concluded that during an Omicron period (December 2021-March 2023) in Ireland, the COVID-19 vaccination programme prevented COVID-19 related illness including ICU admissions and deaths due to COVID-19. Vaccination therefore protected population health and the healthcare system. The benefits of vaccination are ongoing, emphasising the importance of vaccination.

References

1. Sacco C, Mateo-Urdiales A, Petrone D, Spuri M, Fabiani M, Vescio MF, et al. Estimating averted COVID-19 cases, hospitalisations, intensive care unit admissions and deaths by COVID-19 vaccination, Italy, January−September 2021. Eurosurveillance. 2021;26(47):2101001.
2. Meslé MM, Brown J, Mook P, Hagan J, Pastore R, Bundle N, et al. Estimated number of deaths directly averted in people 60 years and older as a result of COVID-19 vaccination in the WHO European Region, December 2020 to November 2021. Eurosurveillance. 2021;26(47). 10.2807/1560-7917.es.2021.26.47.2101021
3. VIEW-Hub. [Available from: https://view-hub.org/resources].