9 strains HPV types covered by Gardasil 9: 6, 11, 16, 18, 31, 33, 45, 52, 58 — types 16 and 18 alone cause 70% of cervical cancers
14,000 New cervical cancer diagnoses per year in the US — 90% are caused by HPV; vaccination of pre-sexual adolescents is projected to eliminate most cases
Up to 45 Age to which Gardasil 9 is FDA-approved (since 2018) — though routine recommendation only applies to ages 9–26; 27–45 is individual decision-making

What HPV is and why it matters

Human papillomavirus is the most common sexually transmitted infection — most sexually active people will have at least one HPV type at some point. Most infections clear on their own within two years. The ones that don't, particularly persistent infections with high-risk strains, can lead to precancerous cervical cell changes and, eventually, cervical cancer.

HPV also causes cancers of the vulva, vagina, anus, throat, and mouth. Gardasil 9 covers the strains responsible for approximately 70% of cervical cancers (types 16 and 18), plus five more cancer-associated strains, plus types 6 and 11 which cause 90% of genital warts.

Why age at vaccination matters so much

The vaccine works by priming your immune system to recognise these HPV strains before you're exposed to them. Once you've already been infected with a given strain, vaccination provides no protection against that strain — it can't clear an existing infection or reverse cellular changes already caused by it.

This is why vaccination in pre-sexual adolescence produces the strongest benefit: most people in that age group haven't yet been exposed to any of the covered strains. Real-world data from the UK's vaccination programme, which began in 2008, is remarkable: cervical cancer rates in vaccinated cohorts have dropped by more than 87%.

By the time most women reach their late 20s or 30s, they've likely been exposed to at least some covered strains — which is why benefit decreases with age. That said, few women have been exposed to all nine strains covered. For women who haven't had many sexual partners or who have not been sexually active for significant periods, vaccination can still provide meaningful protection against strains they haven't yet encountered.

The guidelines for women over 26

In the US, CDC guidelines recommend routine HPV vaccination for everyone through age 26. For ages 27–45, the recommendation is "shared clinical decision-making" — not a routine recommendation, because population-level benefit is lower in this group, but a conversation with your doctor about your specific situation.

Women in this age group who may benefit most: those who have been in long-term monogamous relationships and have limited prior exposure, those who are newly single, those who are immunocompromised (as the immune response is more variable), or those in populations with lower prior vaccination rates.

Practical tip

You don't need HPV testing before deciding whether to vaccinate. Current guidelines do not recommend testing first — even if you have HPV, you may not have all nine covered strains. If you're under 45 and haven't been vaccinated, raise it at your next GP or gynaecology appointment and have the conversation about whether it makes sense for you.

Research note

The FUTURE II trial and subsequent studies establishing Gardasil's efficacy were conducted primarily in young women. For the 27–45 age extension (VIVIANE trial), efficacy against new HPV infections was demonstrated — supporting the FDA approval — but the proportion of participants already exposed to covered strains was significantly higher, which is why routine recommendations stop at 26.

The vaccine and cervical screening

This is the part most women don't know: vaccination does not replace cervical screening. The vaccine covers nine strains — but there are over 100 known HPV strains, and around 14 high-risk ones. Smear tests (cervical screening) catch abnormal cell changes regardless of which strain caused them.

Even women who received the vaccine as teenagers still need regular cervical screening according to their national guidelines. In England, that's every three years from age 25 (or every five years with an HPV test). In the US, recommendations vary by age and test type. Keep those appointments. The vaccine and the smear test together provide the strongest protection.

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If you're not sure whether you've been vaccinated

Many women who were in secondary school in the 2000s in the UK received an older version (Cervarix) which covered only two strains. If you received Cervarix and are under 45, the expanded protection offered by Gardasil 9 is worth discussing with your GP. Keep up to date with cervical screening regardless of vaccination history.

Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before making changes to your health routine.

References

  1. CDC. HPV Vaccination Recommendations. CDC.gov
  2. FDA. Gardasil 9 Approval for Ages 27–45. 2018. FDA NDA 125508/S-016.
  3. Falcaro M, et al. The effects of the national HPV vaccination programme in England: a retrospective observational study. The Lancet. 2021;398(10316):2084–2092. PubMed
  4. Castellsague X, et al. VIVIANE study: HPV vaccine efficacy in adult women 25–45. The Lancet Infectious Diseases. 2011;11(10):751–759.