1. Home>
2. Specialties>
3. Infectious Diseases>
4. Summary and Comment

Who Should Receive Flu Vaccine?

A mathematical model incorporating transmission dynamics suggests that priority be given to immunizing schoolchildren and adults aged 30 to 39.

Decisions about allocation of influenza vaccines have been based mainly on disease incidence and complications, with secondary consideration given to potential years of life lost and economic costs. A concern that has received less attention is the effect of vaccination on transmission dynamics. Now, researchers have created a mathematical model that includes mortality patterns from the 1918 and 1957 influenza pandemics and age-specific interpersonal contact rates to determine optimal influenza immunization strategies for the U.S. They assessed the effect of various strategies using five outcome measures: total infections averted, total deaths averted, years of life lost, "contingent valuation" (the "disutility" of death at each age), and economic costs.

In an initial assessment, the optimal vaccine distribution for all outcomes for both the 1918 and 1957 scenarios involved immunizing children aged 5 to 19 years and adults aged 30 to 39. Vaccine efficacy was linked to a reduction in transmission among children, as well as from children to their parents, who serve as a bridge to the rest of the population. If vaccine supply was limited, this age-specific strategy remained optimal for all outcome measures in the 1918 scenario. However, in the 1957 scenario, assuming 37 million doses, the outcome measure of total deaths would give priority to immunizing adults aged 65; at 36 million doses, the contingent-valuation outcome would shift priority to people aged 45 to 49 because of the economic productivity and greater severity of infection in this group. The model also allowed analysis of the effect of differences in vaccine efficacy and in the relative communicability of influenza strains; in general, variations in these parameters did not substantially alter optimal vaccine allocation.

Comment: Unfortunately, this model does not consider the benefit of vaccinating high-risk individuals across all age groups, either directly to these individuals or to other high-risk people with whom they are in contact in healthcare settings. In addition, implementing the "optimal" vaccination strategy would be difficult in the current U.S. healthcare environment. Still, the findings indicate the importance of considering age-specific transmission dynamics when developing influenza immunization strategies.

— Richard T. Ellison III, MD

Published in Journal Watch Infectious Diseases September 2, 2009

Citation(s):

Medlock J and Galvani AP. Optimizing influenza vaccine distribution. Science 2009 Aug 20; [e-pub ahead of print]. (http://dx.doi.org/10.1126/science.1175570)

2011 Top Stories