Concurrent Infection With Multiple Human Papillomavirus Types Among Unvaccinated and Vaccinated 17-Year-Old Norwegian Girls

Abstract

Background: Whether type-specific human papillomavirus (HPV) infection influences the risk of acquiring infections with other HPV types is unclear. We studied concurrent HPV infections in 17-year-old girls from 2 birth cohorts; the first vaccine-eligible cohort in Norway and a prevaccination cohort.

Methods: Urine samples were collected and tested for 37 HPV genotypes. This study was restricted to unvaccinated girls from the prevaccination cohort (n = 5245) and vaccinated girls from the vaccine-eligible cohort (n = 4904). Risk of HPV infection was modelled using mixed-effect logistic regression. Expected frequencies of concurrent infection with each pairwise combination of the vaccine types and high-risk types (6/11/16/18/31/33/35/39/45/51/52/56/58/59) were compared to observed frequencies.

Results: Infection with multiple HPV types was more common among unvaccinated girls than vaccinated girls (9.2% vs 3.7%). HPV33 and HPV51 was the only HPV pair that was detected together more often than expected among both unvaccinated (P = .002) and vaccinated girls (P < .001). No HPV pairs were observed significantly less often than expected.

Conclusions: HPV33 and HPV51 tended to be involved in coinfection among both unvaccinated and vaccinated girls. The introduction of HPV vaccination does not seem to have had an effect on the tendency of specific HPV types to cluster together.

Keywords: HPV genotype; HPV vaccine; Luminex assay; epidemiological monitoring; human papillomavirus; multiple infections; urine sample.

Figure 1.

Type-specific human papillomavirus (HPV) prevalence among 5245 unvaccinated girls born in 1994 (A) and 4904 vaccinated girls born in 1997 (B).

Figure 2.

Occurrence of concurrent infection with each possible pairwise combination of high-risk and vaccine human papillomavirus types (6, 11, 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, and 59) among 5245 unvaccinated girls born in 1994 (A) and 4904 vaccinated girls born in 1997 (B). Mixed-effect logistic regression was used to calculate expected number of girls. Pairs with a significant deviation between the observed and expected number (P < .05) are represented in red.

Figure 3.

Associations between pairs of human papillomavirus types according to percent identity in the L1 region. Abbreviations: CI, confidence interval; OR, odds ratio.

Figure 4.

Associations between pairs of HPV types according to carcinogenicity. HR types: 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, and 59; non-HR types: 6, 11, 30, 40, 42, 43, 53, 54, 61, 66, 67, 68, 70, 73, 74, 81, 82, 83, 86, 87, 89, 90, and 91. Abbreviations: CI, confidence interval; HPV, human papillomavirus; HR, high risk; OR, odds ratio.