Impacts of human papillomavirus vaccination for different populations: A modeling study

Abstract

International variations in the prevalence of HPV infection derive from differences in sexual behaviors, which are also a key factor of the basic reproductive number (R0) of HPV infection in different populations. R 0 affects the strength of herd protection and hence the impact of a vaccination program. Similar vaccination programs may therefore generate different levels of impact depending upon the population's pre‐vaccination HPV prevalence. We used IARC's transmission model to estimate (i) the overall effectiveness of vaccination versus no vaccination in women aged 15–34 years measured as percent prevalence reduction (%PR) of HPV16 and (ii) the corresponding herd protection in populations with gender‐equal or traditional sexual behavior and with different levels of sexual activity, corresponding to pre‐vaccination HPV16 prevalence from 1 to 8% as observed worldwide. Between populations with different levels of gender‐equal sexual activity, the highest difference in %PR under girls‐only vaccination is observed at 40% coverage (91%PR vs. 48%PR for 1% and 8% pre‐vaccination prevalence, respectively). HPV16 elimination is obtained with 55 and 97% coverage, respectively. To achieve desirable levels of HPV16 prevalence after vaccination, different levels of coverage are required in populations with different levels of pre‐vaccination HPV16 prevalence, for example, in populations with gender‐equal sexual behavior a decrease to 1/1000 HPV16 from pre‐vaccination prevalence of 1 and 8% would require coverages of 37 and 96%, respectively. In traditional populations, corresponding coverages would need to be 28 and 93%, respectively. In conclusion, pre‐vaccination HPV prevalence strongly influences herd immunity and helps predict the overall effectiveness of HPV vaccination.

Assessment of herd effects among women and heterosexual men after girls‐only HPV16/18 vaccination in the Netherlands: A repeated cross‐sectional study

“…The results are therefore not representative of the general Dutch population, probably underestimating the impact of vaccination. 20 The decrease in the HPV16/18 prevalence among women in our study, coincided with an increase in the percentage of women who reported to be vaccinated. After adjustment for vaccination status, the HPV16/18 prevalence did not differ in 2015 as compared to 2009, indicating that the increasing proportion of vaccinated women explained the decreasing HPV prevalence.…”

“…Last, we used a population of visitors to STI clinics who are at higher HPV risk as compared to the general population. The results are therefore not representative of the general Dutch population, probably underestimating the impact of vaccination …”

“…There are several possible explanations for the absence of a declining trend among unvaccinated women in our study. First, in high‐risk populations with frequent changes in sex partners, people are more likely to encounter a HPV‐positive man or women, limiting herd effects . However, in Australia declines in vaccine‐type prevalence were also observed among the high‐risk group of chlamydia‐positive unvaccinated women .…”

“…First, in high-risk populations with frequent changes in sex partners, people are more likely to encounter a HPV-positive man or women, limiting herd effects. 20 However, in Australia declines in vaccine-type prevalence were also observed among the high-risk group of chlamydia-positive unvaccinated women. 33 Second, in Australia and Scotland, the vaccination initiation rate was much higher: over 80% in Australia and over 90% in Scotland.…”

Assessing the Long-Term Role of Vaccination against HPV after Loop Electrosurgical Excision Procedure (LEEP): A Propensity-Score Matched Comparison

“…Through the implementation of screening methods (including pap-smear and HPV DNA testing), most pre-neoplastic lesions were detected and treated before the onset of invasive cancer, thus reducing the burden of cervical cancer [ 3 ]. Interestingly, the recent adoption of primary prevention (i.e., vaccination) aims to eradicate HPV and HPV-related lesions [ 4 ]. Modeling studies showed that the widespread adoption of vaccination would reduce the incidence of HPV related lesions, dramatically [ 4 , 5 ].…”