Source: Infectious Disease Advisor
Date: September 30th, 2019
Author: Zahra Masoud

Oral human papillomavirus (HPV) prevalence has decreased in unvaccinated men, possibly as a result of herd protection, but the incidence of such infection has remained unchanged in unvaccinated women from 2009 to 2016 in the United States, according to a study published in the Journal of the American Medical Association.

Since 2011 for women and 2006 for men, prophylactic HPV vaccination for prevention of anogenital HPV infection has been recommended for routine use in the United States. Previous studies have demonstrated that this vaccine has high efficacy in reducing the prevalence of oral HPV infection. However, the vaccine is not indicated to prevent oral HPV infection or oropharyngeal cancers because there are few results from randomized trials. Further, there has been a lack of surveillance studies reporting on herd protection against oral HPV infection, which is defined as a form of indirect protection from infectious diseases that occurs when a large percentage of the population has become immune/vaccinated, thereby providing protection for individuals who are not immune/not vaccinated. Therefore, this study investigated evidence for herd protection against oral HPV infection in unvaccinated men and women in the United States using temporal comparisons of oral HPV prevalence for 4 vaccine types and 33 non-vaccine types.

This study was conducted across 4 cycles (from 2009 to 2016) of the National Health and Nutrition Examination Survey (NHANES), using a cross-sectional, stratified, multistage probability sample of the civilian population in the United States. For the examination component, response rates were 68.5% in the 2009 to 2010 period, 69.5% in the 2011 to 2012 period, 68.5% in 2013 to 2014, and 58.7% in 2015 to 2016. In total, 13,676 participants were included, which represented 174,333,042 individuals in the US population aged 18 to 59 years. The 4 vaccine-type oral HPV were HPV-16, -18, -6, and -11. DNA was collected from oral rinses and was evaluated using PGMY09/11 polymerase chain reaction and linear array genotyping for 37 types of HPV presence. In unvaccinated individuals, sex-stratified analyses were performed along with multivariable logistic regression analyses adjusted for other variables.

From 2009 to 2016, HPV vaccination rates increased from 0% to 5.8% in men and from 7.3% to 15.1% in women. From 2009 to 2010 to 2015 to 2016, vaccine-type oral HPV prevalence declined from 2.7% to 1.6% (P =.009) in unvaccinated men; however, this decline was not heterogenous by age (P =.41 for interaction). During this period, non-vaccine-type oral HPV prevalence remained unchanged (P =.66) among unvaccinated men. From 2009 to 2010 to 2015 to 2016 in unvaccinated women, both vaccine-type and non-vaccine-type oral HPV prevalence remained unchanged (P =.79 and P =.58, respectively).

The 37% decline in vaccine-type oral HPV among unvaccinated men from 2009 to 2016 suggests herd protection against oral HPV infections. This herd protection may arise from the increased rate of HPV vaccination among women and is consistent with herd protection studies against genital HPV infections in unvaccinated women in the United States. The unchanged prevalence of oral HPV among unvaccinated women from 2009 to 2016 does not suggest herd protection; this may reflect low statistical power because of a low prevalence in women.

Overall, the study authors concluded that, “The estimated herd protection should be incorporated into evaluations of cost-effectiveness of HPV vaccination of men older than 26 years. Vaccine trials of oral HPV incidence and persistence in men should inflate sample sizes to account for herd protection.”

Reference

Chaturvedi AK, Graubard BI, Broutian T, Xiao W, Pickard RK, Kahle L, Gillison ML. Prevalence of oral HPV infection in unvaccinated men and women in the United States, 2009-2016. JAMA. 2019;322(10):977-979.