By Dr. Monika Naus, Medical Director, Immunization Programs and Vaccine Preventable Diseases Services, BC Centre for Disease Control
The HPV (Human Papilloma Virus) vaccine program for grade 6 boys started in BC with the 2017/18 school year. This program will accompany the program for grade 6 girls who have been eligible since September 2008. While these programs are delivered in school based clinics by public health nurses, many studies have shown that a recommendation from a trusted physician provider is strongly associated with the decision to vaccinate. Uptake of HPV vaccine for grade 6 girls remains lower than for other school based immunization programs. The inclusion of boys in the routine grade 6 program provides an opportunity for physicians to stress the importance of this vaccine for both genders, answer any questions that parents or kids may have, and give their recommendation in support of vaccination.
The vaccine that will be used in the BC program is the 9-valent HPV vaccine (HPV9 or Gardasil 9, Merck Canada Inc.) which was introduced into the program for girls in September 2016 and has replaced the use of the 4-valent vaccine for all aspects of the BC program, including the high-risk male program. This vaccine is approved by Health Canada for boys and men aged 9-26 years for prevention of anogenital warts, anal cancer, and pre-cancerous lesions. Similar to use in girls, a schedule of only 2 doses given 6 months apart is approved for use in boys who start a series prior to their 15th birthday. This recommendation is based on a non-inferior immune response to 2 doses in this age group compared to 3 doses in older cohorts. Clinical trials of HPV 4-valent vaccine in 16-26 year old females and males, as well as men who have sex with men, and of HPV9 in females, have demonstrated high efficacy. HPV9 efficacy has been >90% and comparable to that of HPV4 for the same 4 strains (types 6 and 11 causing genital warts and types 16 and 18 causing the majority of cancers) of the virus for all clinical endpoints, including infection, persistent infection, pre-cancerous lesions, and anogenital warts. For males, the protection offered by the 5 additional oncogenic strains has been tested by immunogenicity, and the antibody responses are similar to those against the 4 original strains in the vaccine. Duration of protection following 3 doses has been demonstrated out to 10 years and because the antibody kinetics following a 2-dose schedule are similar, it is expected that a two dose series will also provide long lasting protection.
Estimates of the attributable fraction of HPV strains causing anal cancers in North American males are about 89% for HPV 16 and 18, and an additional 9% for the other 5 strains (types 31,33, 45, 52, 58). HPV is also responsible for about 50% of penile, 35% of oropharyngeal (largely HPV type 16) and 25% of oral cavity cancers, with alcohol or tobacco responsible for the larger portion of oropharyngeal and oral cavity cancers. There is expectation that future studies will demonstrate protection from HPV-related disease at non-genital/anal sites. HPV vaccine safety has been well studied and safety has been demonstrated. The 9-valent vaccine is associated with a higher rate of injection site reactions than the 4-valent vaccine, attributable to a higher antigen content and higher concentration of the aluminum adjuvant.
Contact Dr. Monika Naus at Monika.Naus@bccdc.ca