HPV vaccination

Acquisition and persistence of HPV is the major step in developing cervical cancer and it is acquired soon after the initiation of sexual intercourse. The lifetime risk for getting HPV in New Zealand is 80%. Most HPV gets cleared by the body, especially in young women (about 80-90% will clear the virus within 2 years of acquisition). 

There are many types of HPV. Types 6 and 11 cause genital warts. Types 16 and 18 are the most oncogenic types- they are responsible for about 70% of cervical cancers. Other types that cause cervical cancer are types 31, 33, 45, 52 and 58. The majority of women who have an infection with a high-risk subtype do not develop cancer. However, in some, cervical cancer will develop- usually 10-20 years after the initial infection. 

HPV vaccination became part of the NZ vaccination schedule in 2004. The initial vaccine was Gardasil 4, which covered types 6, 11, 16, and 18. From 2017, Gardasil 9 has been used. This provides more extensive coverage against high risk, pro-oncogenic HPVs. It covers 6, 11, 16, 18, 31, 33, 45, 52, and 58. The age range for subsidised access to Gardasil 9 for young men and women is ages 9-26 years. 

Vaccine coverage in New Zealand is currently poor, with about 50% of eligible women having the vaccine. There has been a reduction in genital warts cases with the introduction of these vaccines- between 30-50%. In Australia, where the rates of HPV vaccine uptake are >70%, there has been a 90% reduction in genital warts. As cervical cancer usually develops decades after infection, more time will be needed before we can fully evaluate the impact of the vaccine on cervical dysplasia and cervical cancer in New Zealand. In Australia, there has been a 40-50% reduction in high grade changes in women aged <20 years, and a 10% reduction in women 20-24 years. 

Reference: https://bpac.org.nz/2016/hpv.aspx