HPV infections fall dramatically but researchers say vaccine efficacy is 'uncertain'

Cancer-causing HPV16 and 18 infections are now 'extremely uncommon' in young sexually active women in England, according to the latest figures from Public Health England. However, separate research has questioned the efficacy of the HPV vaccine in preventing cervical cancer.

More than 80% of girls in school year 9 have received the recommended two doses of HPV vaccine. | GETTY IMAGES
More than 80% of girls in school year 9 have received the recommended two doses of HPV vaccine. | GETTY IMAGES

Infection rates for HPV16 and 18 are now below 2% in women aged 16 to 18 compared with over 15% in 2008, when routine HPV vaccination was introduced. HPV causes 99% of cervical cancers and types 16 and 18 are responsible for around 80% of cases.

Prevalence of HPV6 and 11, which cause genital warts, also fell for the first time in this group - down from 7–10% between 2010 and 2017, to 4% in 2018.

The prevalence of 3 other cancer-causing types, HPV31, 33 and 45, has also declined, suggesting the vaccine provides substantial cross-protection.

The national HPV vaccination programme was extended to boys in 2019. The current vaccine protects against HPV16, 18, 6 and 11.

Marta Checchi, a senior scientist at Public Health England, said: 'This is now the fifth year of finding less than 2% of young sexually active women infected with HPV16 or 18. These new data demonstrate the huge impact of the vaccination programme in its first 10 years.'

Efficacy questioned

Elsewhere, however, researchers have suggested the efficacy of the HPV vaccine may have been 'overestimated'.

In an analysis of 12 clinical trials, researchers from Newcastle University and Queen Mary University of London say they found insufficient data to clearly conclude that HPV vaccine prevents the cell changes that can eventually develop into cervical cancer.

The analysis, published in the Journal of the Royal Society of Medicine, included published phase II and III randomised controlled efficacy trials of the HPV vaccines Cervarix and Gardasil.

Although the team found evidence that vaccination prevents low-grade abnormal cell changes, they said this is not clinically important because these often resolve spontaneously - and that evidence of efficacy against low-grade cell changes does not necessarily indicate efficacy against the high-grade changes most likely to progress to cancer.

They also highlighted other 'methodological problems' with the trials, including the choice of participants, which they criticised as not being representative of vaccination target groups. 

The researchers said: 'It is uncertain whether HPV vaccination prevents cervical cancer as trials were not designed to detect this outcome, which takes decades to develop. For most outcomes, follow-up data exist for an average of only four or five years.'

The researchers warned that attendance at cervical screening - which has been found to prevent more than 80% of cervical cancers - remained essential regardless of vaccination status. 

Clear impact

In response to the study, PHE senior scientist Marta Checchi told GPonline: 'Data from the UK suggests that there has been a decline in five high-risk HPV types that cause around 90% of cervical cancer cases. This means that the vaccine programme is on target to dramatically reduce the number of women being diagnosed with high-grade cervical abnormalities and cervical cancer in the future.'

Dr Ravi Pawa, medical affairs director for Gardasil manufacturer MSD, told GPonline the company believed the study's findings were misleading and could undermine public confidence in the HPV national immunisation programme.

Dr Pawa added: 'The impact of HPV vaccination is clear. It is recommended by the WHO and is recognised as an integral part of cervical cancer elimination plans.'

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