Effectiveness of COVID-19 vaccines against hospitalisation, death and infection over time in Aotearoa New Zealand: a retrospective cohort study

As Aotearoa transitioned to a COVID-19 mitigation strategy, real-world vaccine effectiveness (VE) data became vital. This retrospective cohort study (Dec 2020–Feb 2023) assessed VE against hospitalisation, death and infection during the Omicron period. Second booster VE against hospitalisation was 81.8% at one month, declining to 49.0% by six months. VE against death remained high at 87.2% up to six months post-booster. Protection against infection was moderate but sustained. These findings highlight the importance of booster doses and provide critical evidence to guide vaccination policy and preparedness for future COVID-19 waves in NZ.