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. 2015 Jul 28;10(7):e0134185.
doi: 10.1371/journal.pone.0134185. eCollection 2015.

The Participation of HPV-Vaccinated Women in a National Cervical Screening Program: Population-Based Cohort Study

Eva Herweijer  1 , Adina L Feldman  2 , Alexander Ploner  1 , Lisen Arnheim-Dahlström  1 , Ingrid Uhnoo  3 , Eva Netterlid  4 , Joakim Dillner  5 , Pär Sparén  1 , Karin Sundström  6
Affiliations

The Participation of HPV-Vaccinated Women in a National Cervical Screening Program: Population-Based Cohort Study

Eva Herweijer et al. PLoS One. .

Abstract

Background: Concerns have been raised that HPV-vaccination might affect women's cervical screening behavior. We therefore investigated the association between opportunistic HPV-vaccination and attendance after invitation to cervical screening.

Methods: A cohort of all women resident in Sweden, born 1977-1987 (N=629,703), and invited to cervical screening, was followed October 2006 - December 2012. Invitations to screening were identified via the National Quality Register for Cervical Cancer Prevention, as was the primary outcome of a registered smear. Vaccination status was obtained from two nationwide health data registers. Hazard ratios (HR) were estimated using Cox regression adjusted for age, education level and income (HRadj). Women were individually followed for up to 6 years, of which the first and second screening rounds were analyzed separately.

Results: Screening attendance after three years of follow-up was 86% in vaccinated women (N=4,897) and 75% in unvaccinated women (N=625,804). The crude HR of screening attendance in vaccinated vs. unvaccinated women was 1.31 (95% CI 1.27-1.35) in the first screening round. Adjustment for education and income reduced but did not erase this difference (HRadj=1.09, 95% CI 1.05-1.13). In the second screening round, attendance was likewise higher in HPV-vaccinated women (crude HR=1.26, 95% CI 1.21-1.32; HRadj=1.15, 95% CI 1.10-1.20).

Conclusions: HPV-vaccination is so far associated with equal or higher attendance to cervical screening in Sweden in a cohort of opportunistically vaccinated young women. Most but not all of the difference in attendance was explained by socioeconomic differences between vaccinated and unvaccinated women. HPV vaccine effectiveness studies should consider screening attendance of HPV-vaccinated women when assessing incidence of screen-detected cervical lesions.

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Conflict of interest statement

Competing Interests: The authors of this manuscript have the following competing interests: KS and JD have received unconditional grants for other studies from Merck and Sanofi Pasteur Merck Sharp & Dohme; PS has received unconditional grants for other studies and honoraria from GlaxoSmithKline; LAD has received unconditional grants for other studies from GlaxoSmithKline, Merck, and Sanofi Pasteur Merck Sharp & Dohme; Eva Netterlid reports other relationships related to the Swedish HPV Vaccination Register (SVEVAC). SVEVAC, originally developed at the Public Health Agency of Sweden (formerly the Swedish Institute for Communicable Disease Control), is currently funded by the Swedish Association of Local Authorities and Regions. In the start-up phase of the registry, sponsoring was also received from Sanofi Pasteur Merck Sharp & Dohme and GlaxoSmithKline, and for a period a minor part of EN’s salary came from these funds. The authors confirm that the information included in the Competing Interests section does not alter their adherence to PLOS ONE policies on sharing data and materials.

Figures

Fig 1
Fig 1. Details on study exclusions and population analyzed to study the association between HPV vaccination status and attendance to cervical screening after invitation.
Fig 2
Fig 2. Age at opportunistic HPV vaccination among HPV-vaccinated females in the study cohort.
Fig 3
Fig 3. Cumulative incidence proportions of screening attendance since first invitation to screening by vaccination status.
See this image and copyright information in PMC

References

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