We anticipated that moderate human papillomavirus (HPV) vaccination in
the Finnish community-randomized trial will demonstrate changes in ecological niche
of the circulating HPVs such as the niche occupation by non-vaccine-covered HPV
types. In this study we exploited a re-randomized cervical screening trial that had been
launched in 2014 among 14,686 HPV-vaccinees starting from 22-year-old omen, born
in 1992 (refer to Chapter V). Approximately half of the HPV-vaccinees, 6,958 women
participated the trial and provided serial cervical samples for HPV typing at ages 22, 25
and 28 years. With the trial follow-up we could verify the more (gender-neutral
vaccination arm) or less (girls-only vaccination arm) efficient vacation of ecological
niche initially occupied by the vaccine-covered HPV types 16/18/31/45 up to eight
years post-vaccination. However, no consistent changes were observed neither in the
gender-neutral arm nor in the girls-only arm in epidemiological analyses for the nonvaccine-covered HPV39/51/52/56/58/59/66/68/73 determined by PCR of cervical
samples or by serology. In contrast, our analyses at the community level revealed rising
ecological diversity of the more or less non-vaccine-covered HPV types
33/35/51/52/56/58/59 in gender-neutral vaccination communities with a stronger herd
immunity compared with girls-only vaccination communities from four to eight years
post vaccination. This is probably the first recorded sign of niche occupation by the
non-vaccine-targeted HPV types post-population level vaccination.
Keywords: Alpha-diversity, beta-diversity, ecology, human papillomavirus, prevalence, seroprevalence, Shannon-index, type-distribution.