Why is HPV vaccination not routinely recommended for all adults age 27 through 45 years?

Because HPV acquisition generally occurs soon after first sexual activity, vaccine effectiveness will be lower in older age groups as a result of prior infections. In general, exposure to HPV also decreases among individuals in older age groups. Evidence suggests that although HPV vaccination is safe for adults 27 through 45 years, population benefit would be minimal; nevertheless, some adults who are unvaccinated or incompletely vaccinated might be at risk for new HPV infection and might benefit from vaccination in this age range.