Routine vaccination of girls aged 12 or 13 years with the human papillomavirus (HPV) vaccine in Scotland has led to a dramatic reduction in cervical disease in later life, according to a UK study.
Unvaccinated women also showed a reduction in disease, possibly due to herd protection, said the researchers in the British Medical Journal.
“The bivalent vaccine is confirmed as being a highly effective vaccine”
They said previous studies have suggested that vaccination protects against the most carcinogenic HPV types 16 and 18, which are responsible for 70% of cervical cancer cases globally.
However, the researchers of the new study highlighted that population data on the effect of routine vaccination on disease was previously lacking.
In line with the rest of the UK, in 2008 Scotland introduced a national HPV immunisation programme for girls aged 12 and 13, with a catch-up programme up to age 18.
University of Edinburgh researchers measured the impact of routine vaccination of girls with the bivalent HPV vaccine on levels of abnormal cells and cervical lesions – known as cervical intraepithelial neoplasia or CIN).
CIN is divided into grades – CIN1, 2+ or 3+. The higher the number, the higher the risk is of developing invasive cancer.
They analysed vaccination and screening records for 138,692 women born between 1988 and 1996 who had a screening test result recorded at age 20 – the age of invitation to first cervical screening in Scotland until mid 2016, when the starting age was raised to 25 years.
Data included unvaccinated women born in 1988-90, women eligible for catch-up vaccination at age 14-17 who were born in 1991-94, and those born in 1995-96 and routinely vaccinated at age 12-13.
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The study found that, compared with unvaccinated women born in 1988, vaccinated women born in 1995 and 1996 showed an 89% reduction in CIN grade 3 or worse, an 88% reduction in CIN grade 2 or worse, and a 79% reduction in CIN grade 1.
Younger age at vaccination was associated with increasing vaccine effectiveness – 86% for CIN grade 3 or worse for women vaccinated at age 12-13 compared with 51% for women vaccinated at age 17.
Unvaccinated women also showed a reduction in disease, suggesting that interruption of HPV transmission in Scotland has created substantial herd protection, said the researchers.
They noted that the analysis was confined to women who attended cervical screening at age 20, possibly leading to over-estimation of vaccine effectiveness.
The study authors said: “Routine vaccination of girls aged 12-13 years with the bivalent HPV vaccine in Scotland has led to a dramatic reduction in preinvasive cervical disease.
“Evidence of clinically relevant herd protection is apparent in unvaccinated women,” they said. “These data are consistent with the reduced prevalence of high risk HPV in Scotland.”
They added: “The bivalent vaccine is confirmed as being a highly effective vaccine and should greatly reduce the incidence of cervical cancer.”