What the vaccine prevents
Human papillomavirus is extremely common - most sexually active adults are infected at some point, usually clear it without ever knowing, and come to no harm. A minority of infections persist, and persistent infection with certain high-risk types is what causes almost all cervical cancer.
It is not only cervical. The same types drive a substantial share of anal, penile, vaginal, vulval and oropharyngeal cancers, which is why the UK programme has covered boys as well as girls since 2019. Gardasil 9 covers nine types, including the two behind most genital warts.
The free routes, which are wider than people think
It is given in school at twelve to thirteen. Anyone who missed it can still get it free on the NHS up to their twenty-fifth birthday - that catch-up is widely underused, and it is the first thing to check.
Separately, men who have sex with men are offered it free through sexual health and HIV services up to forty-five. Neither route costs anything, and both are better value than paying us.
Who it still helps after exposure
The vaccine works best before any exposure, which is why it is given to children. That does not make it pointless afterwards: it covers nine types, and almost nobody has been exposed to all nine.
It does not treat an infection you already have, and it does not replace cervical screening. Screening still finds the changes that vaccination did not prevent, and anyone eligible should keep going whatever their vaccination history.

