Research by the University of British Columbia and the Child & Family Research Institute has led two international bodies to endorse reducing the dosage of the Human Papillomavirus (HPV) vaccine, a move likely to make the vaccine more affordable to low-income countries and increase usage in industrialized nations.
In separate moves this month, the World Health Organization and the European Commission endorsed a schedule of two doses of the HPV vaccine to girls – once between the ages of 9 and 13, and then six months later. Until now, the recommended practice was to give three shots – an initial one, then another two months later and a third injection four months after that. The EC decision was based on a recommendation from the European Medicines Agency in February.
HPV is the most common sexually transmitted infection in North America and the most common cause of cervical cancer in adult years. Use of the vaccine, which was introduced in 2006, varies widely among adolescent girls, from about 30 per cent in the U.S. to about 90 per cent in Quebec and the Maritime provinces. In B.C., participation is about 70 per cent.
The major obstacles to more widespread use is cost, the effort required from health providers and families to administer or receive three doses in a six-month period, and hesitation by some parents that it is not appropriate for their daughters.
B.C. researchers, led by Simon Dobson, a Clinical Associate Professor in the Department of Pediatrics, speculated that reducing the number of doses could help with the cost and effort, and proposed a study to determine whether two doses – an initial one and a second six months later – would be enough to provide immunological protection against HPV, at least through adolescence.
The B.C. Ministry of Health, through the Michael Smith Foundation for Health Research, provided funding for the study, which was done in partnership with the BC Cancer Agency and the B.C. Centre for Disease Control. The study was later expanded to Quebec and Nova Scotia after those provinces provided additional support.
The $1.2 million trial, conducted in Vancouver, Quebec City and Halifax, found that girls who received two doses had just as robust an immunological response as those who received three, up to three years following the first dose. The results, published in JAMA in May 2013, were the first peer-reviewed demonstration of the effectiveness of a reduced-dose schedule.
Quebec is already using just two doses of the vaccine, along with current or planned use in the U.K., the Netherlands, France, Switzerland, Spain, South Africa and Chile.
B.C., based on early results from the UBC-CFRI study, moved to an extended three-dose schedule, with two doses given six months apart in grade 6 and a third dose given in grade 9. In September, the province decided to maintain that schedule until more results on clinical outcomes – not just antibody levels – became available, said Monika Naus, the Medical Director, Immunization Programs & Vaccine Preventable Diseases at the B.C. Centre for Disease Control, and an Associate Professor in the School of Population and Public Health.
Since then, an Australian study showed that a two-dose schedule prevented genital warts – an early marker of HPV infection – in women up to age 21. With that and other studies in mind, the province will likely reconsider its policy soon, Dr. Naus says.
It’s still unknown whether a third dose, years later, might be needed to maintain resistance against HPV into adulthood. UBC and CFRI are now leading a national 10-year study, involving 8,700 participants, to answer that question. To participate, visit the study’s website or call 604-875-2000 ext. 6501, or toll free 1-866-502-2424.
“Everybody knows that when you start a vaccine program, you may have to adjust it as more information becomes available,” says Dr. Dobson, a Clinical Investigator at CFRI and the Vaccine Evaluation Centre, both located at BC Women’s Hospital and Health Centre and BC Children’s Hospital. “That usually means adding a dose. What we’ve done is take a dose away. This will probably make it more acceptable to teen-agers, because who, after all, wants to get an extra shot? But the overwhelming benefit is that it puts the vaccine within the reach of countries that would not normally be able to afford it.”
The reduced dosage might also free up money to expand HPV vaccination to boys, thus helping to protect them against throat and penile cancer and to further protect girls against cervical cancer, Dr. Dobson says.