An agent-based model of the effects of limited vaccination on novel respiratory infections

Vaccination is a safe and effective method for preventing infectious diseases but for novel pathogens vaccine supplies may be limited. We modeled distribution of a limited vaccine supply to specific age groups to investigate the effectiveness at preventing infection and mortality of a novel influenza-like virus.

We used the agent-based modeling platform Framework for Reconstructing Epidemic Dynamics. Limited supplies of vaccine were administered to target age groups. Increased vaccination rates in the 5-17 year old age group tested the ability of single-age group vaccination to interrupt viral transmission. Mortality was estimated using patterns associated with historic pandemic respiratory pathogens.

In all cases limited vaccination had relatively little impact on overall infections. Distribution of vaccine to 5-17 years olds stopped transmission only at very high vaccine coverage, high vaccine effectiveness and relatively low viral transmissibility. The best strategy for decreasing mortality in all modeled scenarios was to target the age group with the highest mortality.

Results suggests that in the event of a highly transmissible disease, limited vaccine supplies will not interrupt transmission. Vaccine distribution protecting the most vulnerable from severe outcomes, even without limiting transmission, was the most effective strategy for preventing mortality.

In the case of an emerging disease, vaccine supplies may be limited during the time of high transmission. In such a situation, vaccinating the age group with the highest transmission rate may not be the best strategy to limit mortality, since it will not stop transmission or produce herd immunity. Vaccination may be better used to target the age group with the highest mortality, which may be different for different diseases.