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Experts welcome new evidence on HPV jab efficacy and safety

Renewed calls to vaccinate boys against HPV as herd immunity not enough to protect them

Louise Prime

Wednesday, 09 May 2018

Experts have welcomed new evidence that prophylactic bivalent and quadrivalent human papillomavirus (HPV) vaccination is effective in reducing the rate of cervical precancer associated with HPV16/18, especially in women vaccinated between 15 and 26 years old and before HPV infection – although longer-term data are still needed regarding any impact on cancer rates – and that the vaccines have a similar rate of serious adverse events as control vaccines. But there have also been renewed calls for the vaccination programme to include boys, who remain vulnerable to HPV infection and associated cancers because they might have sex with male partners, or unvaccinated female partners.

Authors of the Cochrane Review rated the certainty of evidence from 26 trials with a total of 73,428 participants, of which 23 trials addressed vaccine safety and 10 assessed impact on risk of cervical intraepithelial neoplasia grade 2 and above (CIN2+), CIN grade 3 and above (CIN3+), and adenocarcinoma-in-situ (AIS); it looked separately at the effects of vaccines according to participants’ baseline HPV DNA status. Most of the trials were in women under 26 years of age, but three recruited women aged 25 and over.

Cochrane said it found high-certainty evidence that HPV vaccines protect against cervical precancer (CIN2+, CIN3+, and AIS) in adolescent girls and young women aged 15 to 26, particularly for HPV-associated cervical lesions and for girls and women who at baseline were negative for high-risk HPV or HPV16/18 DNA. It found moderate-certainty evidence that HPV vaccines reduce CIN2+ in older women who are HPV16/18 negative – but not when they are unselected by HPV DNA status.

The reviewers found no increased risk of serious adverse effects among vaccinated girls and women. They said the overall number of deaths was low, but there were more deaths among women older than 25 years who received the vaccine – although they were judged not to be related to the vaccine.

They added that the risk of miscarriage and termination were similar between trial arms but increased risk of adverse pregnancy outcomes after HPV vaccination cannot be excluded. They concluded that long-term of follow-up is needed to monitor the impact on cervical cancer, occurrence of rare harms and pregnancy outcomes.

Reaction to the review findings has been overwhelmingly positive. However, it has also led to renewed calls for consideration of a vaccination programme among boys. Emeritus professor of epidemiology at the University of Nottingham Keith Neal said: “The review only looked at cervical precancer (in women and girls), and does not make any comments about whether boys should be given the vaccine too.

“But it is an interesting question – the current argument from UK authorities is that herd immunity will protect boys as well. But this is not completely true because 10% of girls do not get vaccinated, nor does it cover sexual activity when abroad or with arrivals to the UK after the vaccination age. Gay men will never be covered by herd immunity from females, hence the separate programme for gay men to receive the vaccine at GUM clinics. Boys can only be fully protected if all their sexual partners have been vaccinated fully.”

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