Pre-vaccination type-specific HPV prevalence in confirmed cervical high grade lesions in the M(a)over-barori and non-M(a)over-barori populations in New Zealand

Background: New Zealand initiated HPV vaccination in 2008, and has attained 3-dose coverage of similar to 50 % in 12-13 year old girls. Due to the success of program initiatives in M (a) over bar ori girls, higher coverage rates of similar to 60 % have been achieved in this group. We have previously reported a benchmark overall pre-vaccination prevalence of oncogenic HPV infection in high grade cervical lesions in New Zealand. The current extended analysis provides separate pre-vaccination benchmark prevalence for M (a) over bar ori and non-M (a) over bar ori women. Methods: The National Cervical Screening Programme Register (NCSP-R) was used to identify any woman aged 20-69 years of age with an index high grade cytology report from 2009-2011. Extended recruitment was performed until 2012 in clinics with a high proportion of M (a) over bar ori women. Ethnicity status was based on self-reported information by participating women through phone contact supplemented by recordings on the study questionnaire (the NCSP-R was not used to extract ethnicity status). A total of 730 women consented to participate and had a valid HPV test result; 418 of these had histologically-confirmed cervical intraepithelial neoplasia (CIN) 2/3 lesions (149 M (a) over bar ori, 269 non-M (a) over bar ori). The prevalence of any cervical oncogenic HPV infection, HPV16, and HPV18 was calculated in women with CIN2/3. Results: In confirmed CIN2/3, the prevalence of any oncogenic HPV, HPV16 and HPV18 was 96 % (95 % CI: 91-99 %), 54 % (95 % CI: 46-63 %), 11 % (95 % CI: 7-18 %) in M (a) over bar ori and 96 % (95 % CI: 93-98 %), 54 % (95 % CI: 48-60 %), 11 % (95 % CI: 7-15 %) in non-M (a) over bar ori women, respectively. Age-specific patterns of infection for HPV16/18 in confirmed CIN2/3 differed between the two groups (P-interaction = 0.02), with a lower prevalence in younger vs. older M (a) over bar ori women (57 % in 20-29 years vs 75 % in 40-69 years) but a higher prevalence in younger vs. older non-M (a) over bar ori women (70 % in 20-29 years vs 49 % in 40-69 years); the difference in the age-specific patterns of infection for HPV16/18 was not significant either when considering confirmed CIN2 alone (p = 0.09) or CIN3 alone (p = 0.22). Conclusions: The overall prevalence of vaccine-included types in CIN2/3 was similar in M (a) over bar ori and non-M (a) over bar ori women, implying that the long-term effects of vaccination will be similar in the two groups.