What exactly does the HPV vaccine do for your protection against cervical cancer?

HPV types 16 and 18 together cause more than 70% of all cervical cancers. The older bivalent vaccine targets exactly these two types. The newer 9-valent vaccine (Gardasil 9) covers nine types and is estimated to protect against around 90% of all cervical cancers and around 80% of their most serious precancerous stages.

How large that difference is in practice is shown by a major Cochrane analysis of more than 73,000 participants. In girls and women aged 15 to 26 who had not yet been infected, the risk of serious cervical cancer precursors fell from 164 to 2 cases per 10,000. The risk of even more advanced precursors dropped from 70 to virtually zero per 10,000. A Finnish long-term study with eleven years of follow-up found zero cases of invasive HPV-related cancer in the vaccinated group, compared with 17 cases (of which 14 were cervical cancers) among unvaccinated individuals. That study was relatively small, but the outcome is striking.

Age and timing of vaccination make an enormous difference. Vaccination before first sexual contact offers by far the greatest protection; all major international health organisations recommend it preferably before the age of 15. In 2022, the WHO also approved a single-dose schedule as an effective option. In women between 24 and 45 who were already sexually active and were not selected based on their HPV status, no measurable effect on cervical cancer precursors could be demonstrated.

A crucial point: the vaccine is prophylactic -- it prevents new infections but does not clear existing ones. If you already have an HPV infection, the vaccine will no longer help against it. Separate therapeutic vaccines that could do exactly that are under development but not yet available.

There is little cause for concern about safety. The risk of serious side effects was slightly lower in vaccinated individuals than in the control group, not higher. The vaccines contain no live virus, only empty viral shells. Vaccination during pregnancy is routinely advised against, however, because safety data on congenital abnormalities and stillbirth are still limited, even though no increased risk of miscarriage was found. In people with HIV, the vaccine demonstrably produces antibodies, but how long that protection lasts has not yet been sufficiently studied.