Make the human papilloma virus (HPV) vaccine mandatory for boys and optional for girls. Frankly, I'm hesitant to make the HPV vaccine mandatory for anyone, especially for the first five years of use until unforeseen problems can be studied. My bias is to keep such things optional for all, but if mandatory vaccination is to be instituted, I would argue that boys should be required before girls.
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.