Quadrivalent Human Papillomavirus Vaccine Effectiveness: A Swedish National Cohort Study

Abstract

BackgroundIncidence of condyloma, or genital warts (GW), is the earliest possible disease outcome to measure when assessing the effectiveness of human papillomavirus (HPV) vaccination strategies. Efficacy trials that follow prespecified inclusion and exclusion criteria may not be fully generalizable to real-life HPV vaccination programs, which target a broader segment of the population. We assessed GW incidence after on-demand vaccination with quadrivalent HPV vaccine using individual-level data from the entire Swedish population.MethodsAn open cohort of girls and women aged 10 to 44 years living in Sweden between 2006 and 2010 (N > 2.2 million) was linked to multiple population registers to identify incident GW in relation to HPV vaccination. For vaccine effectiveness, incidence rate ratios of GW were estimated using time-to-event analyses with adjustment for attained age and parental education level, stratifying on age at first vaccination.ResultsA total of 124 000 girls and women were vaccinated between 2006 and 2010. Girls and women with at least one university-educated parent were 15 times more likely to be vaccinated before age 20 years than girls and women whose parents did not complete high school (relative risk ratio = 15.45, 95% confidence interval [CI] = 14.65 to 16.30). Among those aged older than 20 years, GW rates declined among the unvaccinated, suggesting that HPV vaccines were preferentially used by women at high risk of GW. Vaccination effectiveness was 76% (95% CI = 73% to 79%) among those who received three doses of the vaccine with their first dose before age 20 years. Vaccine effectiveness was highest in girls vaccinated before age 14 years (effectiveness = 93%, 95% CI = 73% to 98%).ConclusionsYoung age at first vaccination is imperative for maximizing quadrivalent HPV vaccine effectiveness.

To Consent or Decline HPV Vaccination: A Pilot Study at the Start of the National School‐Based Vaccination Program in Sweden

“…Most Western countries have implemented national HPV vaccination programs for young girls, and countries withschool‐based vaccination programs tend to have the highest vaccine uptake 5, 6. To provide the best protection, the vaccine should be administered to young girls7 before they become sexually active 3. In Sweden, all children are offered vaccinations free of charge in the national vaccination program.…”

“…Studies performed in Sweden before the national program was implemented provided conflicting results. For example, Dahlstrom et al14 indicated that parents with a higher level of education were less likely to accept the HPV vaccination, but a register study by Leval et al found the opposite 7. Ethnicity also seems to have a mixed effect on vaccine uptake.…”

Recommended immunization schedules for adults: Clinical practice guidelines by the Escmid Vaccine Study Group (EVASG), European Geriatric Medicine Society (EUGMS) and the World Association for Infectious Diseases and Immunological Disorders (WAidid)

“…42 Similar findings were observed for the quadrivalent HPV vaccine in a study including over 2.2 million females aged 10-44 y, where increased vaccine effectiveness with decreasing age was noted. 43 Together with the fact that 5-15% of sexually active, middleaged adult women acquire a new oncogenic HPV infection each year (1-2% HPV 16/18), 40 these outcomes confirm that midadult women could potentially benefit from the vaccine. However, vaccination in this group of women cannot replace screening.…”

“…[41][42][43][44] However, episodes of mass psychogenic syndrome have been reported and it is therefore important to carefully plan the setting where mass vaccination campaigns will be implemented.…”

Evaluation of the immunogenicity of the quadrivalent HPV vaccine using 2 versus 3 doses at month 21: An epidemiological surveillance mechanism for alternate vaccination schemes

“…6 These vaccines have been incorporated into public vaccination policies with 3 doses schemes administered over a period of 6 months. 7 High effectiveness of the tetravalent vaccine in preventing genital warts has been observed in Sweden 8 and Denmark, 9 and a herd immunity effect has been documented in Australia. 10 In the United States, 4 y after the introduction of a vaccination program, 56% reductions in HPV prevalence have been observed in women between 14 and 19 y of age despite the low coverage rates achieved for the second and third doses.…”