Overlooked Benefits of Vaccination

Should preschoolers get shots for the flu?

When people are vaccinated for infectious diseases like the flu, a benefit accrues to the rest of society. Since those vaccinated are unlikely to spread the disease to those who were not, the unvaccinated are less likely to contract it. As a result, resources aren't expended to care for them and they can avoid lost productivity or even death.

Economists Bryan L. Boulier and Robert S. Goldfarb at The George Washington University in Washington, DC and Tejwant S. Datta at the Einstein Medical Center in Philadelphia, PA, studied these indirect benefits of vaccination--or externalities--by applying epidemiological modeling to simulated scenarios involving influenza and the mumps. They found the benefit of vaccination to the unvaccinated population can far exceed one case prevented per vaccination administered. The findings surpass what many had suspected and could have consequences for vaccination policies, particularly pertaining to influenza and children who often carry the infection home from school.

Vaccinations administered early in influenza outbreaks had particularly high indirect benefits because the vaccine is virtually 100 percent effective and the disease is highly infectious. In the study's simulated populations of 1,000 people, the indirect benefit was greater than one case prevented per influenza vaccination for the first 283 administered. It peaked at 1.58 cases prevented by the 223rd. Thereafter the size of the effect declined.

Mumps is a different story. It is highly contagious and the vaccine is only 80 percent effective. In the simulations, more individuals contract it early on, with one in every five receiving the vaccination continuing to spread the disease. As a result, mumps vaccinations had the highest indirect benefit later in an outbreak. In 1,000 people, mumps vaccinations provided an indirect benefit greater than one case prevented for every vaccination between the 736th and the 815th administered. It peaked at 1.38 cases prevented, then declined, approaching zero by the 1,000th.

The authors suggest externalities of the type they modeled ought to be taken into account by federal recommendations on vaccination, pointing out they often are not part of cost-benefit studies informing current policies. They also do not factor in calculations of the economic impacts of pandemic flu reported by the Centers for Disease Control.

Boulier, Goldfarb and Datta point to the prospects of a pandemic outbreak of influenza and the striking indirect benefit of vaccination as reasons to re-evaluate policy recommendations with a view to vaccinating more children. Current recommendations concentrate on persons at high risk of influenza-related complications or death such as the elderly. This study suggests potentially important benefits to these high-risk populations from vaccinating children. While the findings support the case for more vaccination of children for influenza, it did not support vaccination for healthy young adults. In the case of mumps, the findings support universal vaccination. The study appears in The Berkeley Journal of Economic Analysis & Policy, Volume 1, 2007.