Abstract

In their recent study, Okafor et al provide an important economic evaluation of the monovalent XBB.1.5 COVID-19 booster vaccine relative to no updated booster vaccination in Australia, covering the period from September 2023 to August 2024. They utilized a Markov model from the healthcare system perspective and concluded that booster vaccination remains cost-effective across adult age groups.

Nevertheless, some age-related findings merit closer examination. Notably, Table 2 of their article indicates that healthcare utilization costs decreased considerably by 23% in the 18 to 64 age group but increased modestly by 2% in the 65 to 74 age group, and more substantially by 14% in the group aged 75 years and older. This result appears counterintuitive given that elderly patients had a lower hazard ratio for hospitalization (suggesting greater vaccine effectiveness) compared to younger groups, as shown in their Table 1. Other effectiveness data (such as effectiveness against death or long COVID) were not differentiated by age.