A decreasing incidence of genital warts (GW) can be a first indicator of the effect of HPV vaccination if the qHPV vaccine, which includes HPV types 6 and 11, is used in the population under study. Based on two large cross-sectional surveys in Scandinavia performed before and after licensure of the qHPV vaccine, we examined the self-reported occurrence of GW as well as other sexually transmitted infections (STIs) to evaluate the impact of HPV vaccination with different implementation strategies between the three Scandinavian countries.
In 2004/5 (pre-vaccine) and in 2011/12 (post-vaccine), we conducted two questionnaire-based surveysin Scandinavia (Norway, Sweden and Denmark) among women 18-45 years of age (previously described in details1,2). The questionnaires in both surveys included detailed information about sociodemographic and lifestyle variables, sexual behavior, HPV vaccination and STIs. We assessed the proportions of women reporting to have had GW and other STIs in the pre- and post-vaccination periods; overall and by selected age groups and country.
In the first survey, we included 54,463 women (participation rate 71.3%) and in the second survey 48,788 women (60.6%). Overall, the proportion of women reporting a history of GW was 10.2% and 10.8% respectively in the first and second survey. Considering only the youngest women (18-19 years of age), the proportion in respectively Denmark, Sweden and Norway was 3.3%, 3.5%, 2.8% in the first survey and 1.9%, 3.3%, 2.3% in the second survey. The proportion of women reporting Chlamydia trachomatis and gonorrhea remained the same or increased both overall and in the youngest age groups between the two surveys.
In Denmark where high HPV vaccination coverage was achieved early through the childhood vaccination program, the incidence of GW decreased in the youngest age group targeted by the program. A similar decrease was not observed in Norway and Sweden that had different implementation strategies. The incidences of other STIs remained constant or increased in the meantime, indicating that sexual activity did not decrease between the two surveys.
1. Kjaer SK, Tran TN, Sparén P, Tryggvadottir L, Munk C, Dasbach E, Liaw KL, Nygård J, Nygård M. The burden of genital warts: a study of nearly 70 000 women from the general female population in the 4 Nordic countries. J Infect Dis 2007; 196:1447–1454
2. Hansen BT, Kjær SK, Arnheim-Dahlström L, Liaw KL, Jensen KE, Thomsen LT, Munk C, Nygård M. Human papillomavirus (HPV) vaccination and subsequent sexual behaviour: evidence from a large survey of Nordic women. Vaccine 2014; 32:4945-53. doi: 10.1016/j.vaccine.2014.07.025.