Evidence Mounts for Effectiveness of National HPV Vaccine Program

The quadrivalent HPV vaccine offered significant protection against cervical abnormalities in young Australian women, new study findings show.

The study evaluated data from the population registers in Queensland, Australia, for the four-year period after the introduction of the country’s HPV vaccination program in April 2007. Girls aged 12 to 26 years were eligible for free vaccination. 

Pertinent Points

- The HPV vaccine offered significant protection against cervical abnormalities.

- The number needed to treat with three doses to prevent one cervical abnormality at first screening was 125 for a confirmed high-grade abnormality and
22 for other abnormalities.

The study included 103,353 women. After adjusting for demographic factors, the researchers reported that three doses of the quadrivalent vaccine provided 46% protection against high-grade cervical abnormalities and 34% protection against other cervical abnormalities in women who had not commenced screening prior to vaccination.

The researchers also found that two doses of the vaccine provided 21% protection against both high-grade and other cervical abnormalities. There was no significant protection from one dose.

The high-grade cases included women whose smear test after the vaccine and follow-up biopsy confirmed precancer, defined as a high-grade cervical abnormality. Other cases were defined as women who did not meet the high-grade definition but had other abnormalities. All remaining women whose results came back negative following their smear were assigned to the control group.

The number of women that need to be vaccinated with three doses to prevent one cervical abnormality at first screening round was 125 (95% confidence interval, 97 to 174) for a confirmed high-grade abnormality and 22 (CI, 19 to 25) for other abnormalities.

The researchers concluded that "continued observation of this population is necessary to assess the implications for cervical screening recommendations in the coming era of mass vaccination.”

References:

Crowe E, Pandeya N, Brotherton JML, et al. Effectiveness of quadrivalent human papillomavirus vaccine for the prevention of cervical abnormalities: case-control study nested within a population based screening programme in Australia. BMJ. 2014;348:g1458.