: Can the HPV vaccine be effective if you are already infected? I was just wondering about this subject, when I did a blood exam today and I picked a paper about available vaccines and I saw HPV, the same my mom always bothered

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The HPV vaccine is most effective when preventing you from initial infection. While common, it's possible you haven't been infected with HPV. Even if you are, there is some benefit to still being vaccinated if you're HPV positive. The reason for this is that there are a number of different types of HPV virus, and the vaccine should provide you some protection against types you have not already acquired. From this MMWR report, "Human Papillomavirus Vaccination: Recommendations of the Advisory Committee on Immunization Practices":

In the phase III trials, among females aged 16–26 years who had HPV
vaccine type DNA detected at study enrollment (either seropositive or
seronegative), there was no efficacy against progression to disease or
impact on clearance of infection of that type (114,120). However, HPV4
had 100% efficacy for prevention of CIN2+ attributable to types not
already acquired (120). Among persons seropositive to the relevant HPV
type but HPV DNA-negative, too few cases were detected to evaluate
efficacy, but disease incidence was low and all cases occurred in the
placebo group.

and

HPV vaccination can provide protection against infection with HPV
vaccine types not already acquired. Therefore, vaccination is
recommended through the recommended age for females regardless of
whether they have an abnormal Pap test result, and for females or
males regardless of known HPV infection, HPV-associated precancer
lesions, or anogenital warts. Females who have abnormalities on
cervical cancer screening are likely to be infected with one or more
genital HPV types. With increasing severity of Pap test findings, the
likelihood of infection with HPV 16 or HPV 18 increases (70), and the
expected benefit of vaccination decreases. Females who have had HPV
testing as part of cervical cancer screening might have information
about their HPV status. Males or females with AIN are likely infected
with HPV. The presence of anogenital warts or a history of anogenital
warts indicates present or past infection with HPV, most often HPV 6
or HPV 11. Although vaccination is still recommended, patients should
be advised that vaccination will not have any therapeutic effect on an
existing HPV infection, HPV-associated precancer lesion, cancer, or
anogenital warts.

In short: It is likely still worth getting vaccinated to protect you from other strains of HPV.