The HPV vaccine is most effective when administered before becoming sexually active, providing protection against the types of HPV it targets. However, it still offers benefits for those who are already sexually active and have not been infected with the targeted HPV types. When given to individuals before they engage in sexual activity, the vaccine can prevent nearly all infections caused by the specific HPV strains covered by the vaccine.   For those who are already sexually active, it is possible that they may have been exposed to one or more of the HPV types addressed by the vaccine. While the vaccine might not provide complete protection in such cases, it can still offer valuable benefits. Few young sexually active individuals are infected with all the HPV types prevented by the vaccine, which means that most individuals can still benefit from vaccination and gain protection against the remaining HPV types.