A hypothetical population of 100,000 older adults was included in a Markov model with age ranging from 50 to 85 years to calculate the cost and quality-adjusted life-years (QALYs) gained for vaccination strategies, including: (1) annual influenza vaccine and PPV23 at 50 and 65 years; (2) annual influenza vaccine and PPV23 at 65 years (similar with the current vaccination programme); (3) PPV23 at 50 and 65 years; (4) PPV23 at 65 years; and (5) no vaccination. We evaluated the incremental cost-effectiveness ratio (ICER) and used Monte Carlo simulation for probabilistic sensitivity analysis. The cost-effectiveness threshold was extracted from previous literature.
Pneumococcal infection is a leading cause of morbidity and mortality. We aimed to evaluate the cost-effectiveness of 23-valent polysaccharide vaccine (PPV23) together with influenza vaccination or pneumococcal vaccination alone in adults starting from 50 years vs. 65 years in Hong Kong.
In comparison with no vaccination, all strategies were cost-effective with ICERs less than the threshold (US$24,302 per QALY gained). When compared with no vaccination, strategies 1-4 saved US$ 49.5, US$ 94.9, US$ 584.3, and US$ 1114.2 to gain one QALY respectively. In comparison with strategy 2, strategy 1 spent US$ 195.3 to gain one QALY, whilst strategies 3 and 4 showed less effectiveness with increased costs.
All vaccination strategies were cost-effective, among which the strategy of PPV23 at 50/65 years with annual influenza vaccine was cost-effective even in comparison with current vaccination programme. These findings could help inform the design and implementation of vaccination strategies.