Optimizing the impact of low-efficacy influenza vaccines

PNAS – Proceedings of the National Academy of Sciences of the United States
of America

[Accessed 5 May 2018]

Optimizing the impact of low-efficacy influenza vaccines
Pratha Sah, Jan Medlock, Meagan C. Fitzpatrick, Burton H. Singer, and Alison P. Galvani
PNAS April 30, 2018. 201802479; published ahead of print April 30, 2018. https://doi.org/10.1073/pnas.1802479115
The efficacy of the influenza vaccine against the predominant influenza strain appears to be relatively low during this 2017–2018 season. Our analyses demonstrate the substantial effect of even low-efficacy vaccines in averting infections, hospitalizations, and particularly deaths. Our results also demonstrate that the health burden resulting from influenza is more sensitive to changes to vaccination coverage than to changes to vaccine efficacy. We further determined the uptake distribution of the 140 million doses available that would maximize the effectiveness of vaccination. Our results inform current public health policies and underscore the importance of influenza vaccination.
The efficacy of influenza vaccines varies from one year to the next, with efficacy during the 2017–2018 season anticipated to be lower than usual. However, the impact of low-efficacy vaccines at the population level and their optimal age-specific distribution have yet to be ascertained. Applying an optimization algorithm to a mathematical model of influenza transmission and vaccination in the United States, we determined the optimal age-specific uptake of low-efficacy vaccine that would minimize incidence, hospitalization, mortality, and disability-adjusted life-years (DALYs), respectively. We found that even relatively low-efficacy influenza vaccines can be highly impactful, particularly when vaccine uptake is optimally distributed across age groups. As vaccine efficacy declines, the optimal distribution of vaccine uptake shifts toward the elderly to minimize mortality and DALYs. Health practitioner encouragement and concerted recruitment efforts are required to achieve optimal coverage among target age groups, thereby minimizing influenza morbidity and mortality for the population overall.