HPV: Major new study shows cancer-causing virus 'significantly reduced' after vaccine

Two types of HPV that cause 70% of cervical cancers were significantly reduced after vaccination.

A NEW STUDY has found that HPV vaccination programmes have had a substantial impact in reducing HPV viral infections and precancerous cervical lesions.

The study, conducted by researchers in six countries, combines data over eight years from over 60 million people in high-income countries.

HPV - papillomavirus – is a virus passed between people through skin-to-skin contact. First licensed in 2007, and now used in nearly 100 countries, the HPV vaccine is used to protect against cancers caused by the virus. 

The team of researchers gathered 47 new studies published between February 2014 and October 2018 that compared the frequency of one or more of what are known as HPV endpoints – HPV infections, anogenital wart diagnoses, or microscopically confirmed precancerous cervical lesions.

HPV testing is also used to look for the presence of human papillomavirus in cervical cells. These tests can detect HPV infections that cause cell abnormalities, sometimes even before cell abnormalities are evident.

Smear tests detect abnormal cells that may develop into cancer if they are left untreated. Like the smear test, the HPV test is done on a sample of cells collected from the cervix.

Last September, the HSE confirmed that provisional uptake rate for the HPV vaccine  stood at 70%, an increase of 20 percentage points on the previous year, following declines in previous years after the spread of misinformation about the vaccine.

The vaccine is free for schoolgirls and is expected to become available for boys this year. The vaccine is also available to at-risk groups including men who have sexual contact with men.

The findings 

Combining 65 articles from 14 high-income countries, the researchers gathered data from over 60 million individuals over eight years. 

The research found that the two types of HPV that cause 70% of cervical cancers were significantly reduced after vaccination.

There was an 83% decrease girls aged 13-19 and a 66% decrease in women aged 20-24 years – after five to eight years of vaccination.

Analysing three types of HPV vaccine, the research showed a 54% overall reduction in girls aged 13-19 years.

There were also significant reductions in anal and genital wart diagnoses.

After five to eight years of vaccination, researchers found decreases of 67% in girls aged 15-19, a 54% decrease in women aged 20-24 and a 31% decrease in women aged 25-29.

There was also a 48% reduction in boys aged 15-19 and a 32% reduction in men aged 20-24 years. 

The results also showed that cervical dysplasia – which occurs when abnormal cells grow on the lining of the cervix – decreased significantly five to nine years after HPV vaccination. 

The research team has also reported a 51% reduction in screened girls aged 15-19 years and a 31% reduction in screened women aged 20-24 years. 

‘Strong evidence’ 

There are some limitations to this study, published in the Lancet medical journal today.

The causality between HPV vaccination and changes in the three endpoints can’t be concluded definitively.

The analysis undertaken is based on ecological studies i.e. using aggregated data. 

The author’s believe, however, that their findings “strongly suggest” that the decreases can be attributed to HPV vaccination because larger and faster decreases are observed among cohorts of people targeted for vaccination.

In countries with high vaccination coverage, larger decreases are observed with longer follow-up since the introduction of the HPV vaccination.

There is also currently a lack of data from low and middle-income countries where “the burden of disease” is far greater than in high-income countries, the study notes. 

Researchers have said, however, that the results “provide strong evidence of HPV vaccination working to prevent cervical cancer in real-world settings as both the cause – HPV infection -and precancerous cervical lesions are declining.”

“These results have implications for policy makers around the world as it backs the recently revised [World Health Organisation] position on vaccinating multiple age groups rather than a single cohort when introducing the vaccine.”

Mélanie Drolet of the CHU de Quebec-Laval University Research Center has said that the results “provide strong evidence that HPV vaccination works to prevent cervical cancer in real-world settings as both HPV infections that cause most cervical cancers and precancerous cervical lesions are decreasing.”

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