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Human Papilloma Virus Immunization in Adolescent and Young Adults: A Cohort Study to Illustrate What Events Might be Mistaken for Adverse Reactions

Siegrist, Claire-Anne MD*; Lewis, Edwin M. MPH; Eskola, Juhani MD; Evans, Stephen J. W. MSc§; Black, Steven B. MD

The Pediatric Infectious Disease Journal: November 2007 - Volume 26 - Issue 11 - p 979-984
doi: 10.1097/INF.0b013e318149dfea
Original Studies

Background: The large-scale implementation of human papilloma virus (HPV) immunization will be followed by cases of autoimmune diseases occurring in temporal association with immunizations. To anticipate events that might be mistakenly assumed to be caused by immunization, their prevalence was monitored before vaccine introduction.

Method: Cohort study carried out within a database of female adolescents (n = 214,896) and young adults (n = 221,472) followed in the pre-HPV vaccine era (2005), computing rates of emergency consultations, hospitalizations and outpatient consultations, and estimation of risks of coincident associations.

Results: Immune-mediated conditions were a frequent cause (10.3%) of emergency room consultation by adolescent girls. Nonallergic immune-mediated conditions affected 86 per 100,000, diabetes ranking first. In 2005, 53 per 100,000 adolescents and 389 per 100,000 women were hospitalized for diseases of presumed autoimmune origin, thyroiditis being the most frequent diagnosis. If HPV immunization had been used with 80% coverage, 3 per 100,000 adolescents would have required emergency care for asthma/allergy within 24 hours and 2 per 100,000 for diabetes within 1 week of an injection. The risks of hospitalization in temporal association with immunization are 4 times higher for thyroiditis than for multiple sclerosis or Guillain-Barré's syndrome, and more than 20 times higher in young women than in adolescents.

Conclusion: The distinction between HPV vaccine-caused adverse reactions and events only observed by chance in temporal association is difficult. The prior use of population-based data allows for identification of issues of potential concern, for monitoring the impact of large-scale interventions and for addressing rapidly vaccine-safety issues that may compromise vaccine programs.

From the *Center for Vaccinology and Neonatal Immunology, University of Geneva, Geneva, Switzerland; †Vaccine Study Center and Division of Research, The Permanente Medical Group, Oakland, CA; ‡National Public Health Institute KTL, Helsinki, Finland; §Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London; and ∥Pediatric Infectious Diseases, Stanford University in Palo Alto California, Stanford, CA.

Accepted for publication June 28, 2007.

C.-A.S. received research grant support from Sanofi Pasteur MSD and GlaxoSmithKline for studies unrelated to HPV vaccines and has served on scientific advisory boards concerning issues unrelated to HPV vaccines. S.B.B. and E.M.L. both received research grant support from Merck and GlaxoSmithKline for studies unrelated to HPV vaccine. J.E. and S.J.W.E. have no conflicts of interest to declare.

Address for correspondence: Claire-Anne Siegrist, MD, Center for Vaccinology and Neonatal Immunology, University of Geneva, 1 Rue Michel Servet, 1211 Geneva, Switzerland. E-mail:

© 2007 Lippincott Williams & Wilkins, Inc.