Friday, March 27, 2009

An Interesting Case Study in Public Health Decision Making

Source: "A Vaccine Debate Once Focused on Sex Shifts as Boys Join the Target Market," Rob Stein, The Washington Post, March 26, 2009.

Gardasil, a vaccine, protects against the human papillomavirus (HPV), the most common sexually transmitted infection. HPV causes genital warts and, in women, can lead to cervical cancer -- a disease that strikes about 10,000 American women a year and kills about 3,700.
The virus causes at least 250,000 new cases of genital warts and an estimated 7,500 cancers in males each year, causing perhaps about 1,000 deaths. Vaccinating boys and men would also help prevent the spread of the virus to their sexual partners.......

After the Food and Drug Administration approved the vaccine in 2006 for girls as young as 9, medical authorities recommended that they receive it at age 11 or 12 to protect them before they start having December, Merck asked the FDA to approve the vaccine for males ages 9 to 26.......The relatively pricey vaccine costs about $500 for three shots and the associated office visits.
Comment: This vaccine presents an interesting problem. It is the first case I can think of in which a vaccine was recognized to have different benefits for males than for females.

Any vaccine carries risks to the vaccinated; even when there are large studies of the safety and efficacy of a new vaccine there is a possibility that problems will arise in mass immunization campaigns that were not seen in the research. The public health decision involves comparing the costs and risks of the immunization to the potential benefits. Those benefits include both the benefits to the immunized person, and the benefits to others.

If you can get enough of the population immunized, even the unvaccinated are protected since epidemics are limited. If you can immunize enough people, as was done for smallpox, the disease may be eliminated entirely.

Think also about flu vaccines, which are given to old and sick people who are likely to suffer worse cases of flu if they are infected. In this case, the vaccine is also given to young, healthy people if they might infect a more vulnerable person if they catch the flu.

The HPV vaccine is different in that the direct benefits to males are different than those for females, and one may assume that the indirect benefits in terms of protecting sexual partners and the public are also different. The indirect benefits are especially hard to estimate.

As always in immunization campaigns, there is the problem of conforming individual decisions to the public good. How do you get mothers of young boys to subject their sons to even the small risk of an immunization, and spend the money for the vaccine, in order to provide protection for a possible wife in the distant future?

I suspect this is an especially important public policy issue because its solution will set a pattern for future immunization policy decisions. The genetics of sex are very obvious, but in the future we are going to know a lot more about the genetic makeup of people and how their genome affects their response to vaccines and vulnerability to communicable diseases. We will have lots of situations in which the same vaccine will have different risks and different benefits for different, identifiable groups of people. Making the right decision on immunization policy for boys for the HPV vaccine may help us to make better decisions in many cases in the future.

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