The potential clinical impact and cost-effectiveness of a variant-adapted 2024 Winter and Summer COVID-19 mRNA vaccination campaign in Australia

Objectives To assess the clinical and economic impact, and cost-effectiveness, of a 2024 Winter and Summer COVID-19 Vaccination Campaign (2024 Vaccination Campaign) in Australia compared to no 2024 Vaccination Campaign. Design Modelling study using a COVID-19 susceptible-exposed-infect-recovered (SEIR) dynamic transmission model and a COVID-19 vaccination and infections consequences decision analytic model. Setting, Participants: Australia; Winter 2024 COVID-19 vaccination targeting adults aged ≥18 years, with those aged ≥ 65 years eligible for an additional Summer 2024 dose. Intervention: 2024 Vaccination Campaign using a Moderna variant-updated mRNA vaccine compared to no 2024 Vaccination Campaign. Main outcome measures: Projected number of symptomatic infections, hospitalisation, deaths, and cases of long COVID prevented; quality-adjusted life-years (QALYs) gained, incremental cost of the 2024 Vaccination Campaign, and incremental cost-effectiveness ratio (ICER) of the campaign compared to No Vaccination Campaign. Results Compared to no Vaccination Campaign, a 2024 Vaccination Campaign in Australia is predicted to prevent 241,600 symptomatic infections, 13,500 COVID-19 hospitalisations, 1,200 deaths, and 11,900 cases of long COVID, representing a decrease of 16%, 23%, 26%, and 17%, respectively. This resulted in 19,200 fewer QALYs lost. COVID-19 treatment costs saved with the 2024 Vaccination Campaign was $511.7 million. This partially offset the costs associated with vaccination and adverse event treatment ($1.03 billion), resulting in an incremental 2024 Vaccination Campaign cost of $522 million for a population of 26.3 million, with 4.35 million vaccinations administered. The ICER was $27,100/QALY gained. Increasing the vaccine coverage rate to that observed with influenza vaccination prevented more cases of infection, hospitalisation, and deaths compared to the base case, with an ICER of $34,400/QALY gained. Conclusion Even in the endemic setting with high hybrid immunity, substantial clinical and economic benefits to vaccinating those aged ≥18 years against COVID-19 remain. These benefits may be amplified with increased vaccination coverage. Summary box The known: Vaccination campaigns were a cost-effective strategy to battle the clinical and economic impact of COVID-19 during the pandemic. Even in the endemic setting, COVID-19 continues to cause substantial clinical and economic burden to Australia. The new: Even in a population with high hybrid immunity, COVID-19 vaccination campaigns continue to be cost-effective in Australia in the endemic setting. Clinical benefits are increased by improving the vaccination coverage rate, and not narrowing the targeted population. The implications: In Australia, annual COVID-19 vaccination campaigns should continue. Increasing the COVID-19 vaccination coverage rates and including a broader recommended population is feasible with an acceptable incremental cost-effectiveness ratio.