The purpose of any vaccine is multi-fold: 1) it should protect the individual from getting the disease, 2) the vaccine should protect other contacts from potentially getting infected and 3) a vaccine program can serve to completely eliminate a disease from a population, called “herd immunity”. This has been successfully achieved with small pox, a disease not seen in over 30 years.
Most infectious diseases that are managed with vaccines are transmitted from an infected individual to an unsuspecting host through airborne transmission (influenza, measles, chicken pox, etc), or by exchange of bodily fluids directly (hepatitis, HPV, etc).
Of these, HPV is the only one that is solely transmitted through intercourse and has an effective vaccine. Girls and boys can get this with either voluntary or involuntary (in the case of rape) contact. I would argue that since the boys are the population reservoir for the disease, and are the transmitters to girls or other boys, then only boys should be required to get the vaccine. If a girl transmits the virus to a boy or other girl, the receiver would very likely be a willful participant.
I think that the latest plea for girls to be required to get vaccinated is misguided. From a purely epidemiological standpoint, if anyone is required to get the vaccine, it should be the boys since only they transmit the virus onto others unwillingly (#2 above). Girls should be given the option to be vaccinated for their own protection (#1 above) as well as the protection of their partner (#2). Herd immunity (#3) is not an issue so far with HPV since th virus is endemic.
I know someone will broach the idea of a girl seducing a boy or other girl and therefore transmitting the virus to an unsuspecting host. This argument can be made, but it's very weak. There are many more rapists than seductresses.
ADDENDUM: This has been cross-posted over at dailykos, and as expected, the discussion became quite animated. A few clarifications to the above post came up:
1)The main point is that vaccines serve multiple purposes from a public health standpoint, but compulsory vaccination serves only one purpose, namely, to protect unsuspecting and unwilling others from getting infected from the host. Texas, Michigan, Florida, Maryland and other states are considering making the vaccine mandatory for pre-teen girls, and this makes no sense to me when balancing civil liberties with public health.
2) Should girls get vaccinated? Absolutely, if they and their parents choose. Females are unlikely to pass the virus onto an unsuspecting or unwilling person. Unlike diseases transmitted thru airborne droplet nuclei in public places, HPV is transmitted through genital contact in (presumably) private circumstances. The only times HPV would be transmitted unwillingly would be in the case of rape, which almost always is from male to female or male to male. Therefore, if anybody should undergo compulsory vaccination, it should be males.
3) This sounds counter-intuitive and many at dkos had a problem with the concept of vaccinating the population in order to protect a subgroup of the population. The example of German Measles (Rubella) came up. Rubella is a viral illness that is self-limited and very mild or even asymptomatic in adults and kids. Infection in pregnancy, however, can cause birth defects to the developing fetus in utero, and this will often go undetected until birth. Therefore, from a public health standpoint, we try to vaccinate not only all reproductive age women, but also anybody who may come in contact with susceptible pregnant women. That way, even though some pregnant women may be susceptible, their chances of getting Rubella while pregnant becomes vanishing small because everyone else is vaccinated.