title: An unmasking phenomenon in an observational post-licensure safety study of adolescent girls and young women.
abstract: Our recent experience in a post-licensure safety study of autoimmune conditions following the quadrivalent human papillomavirus vaccine in 189,629 girls and young women ages 9-26 years led us to question the adequacy of the exclusion of Day 0 events to prevent the erroneous association of prevalent conditions with vaccination. Of the 18 confirmed cases of Graves' disease diagnosed in days 1-60 following vaccination, only 6 cases appeared to be truly new onset. Among the remaining 12 cases, 2 cases had abnormal thyroid stimulating hormone or thyroxine labs drawn prior to or on Day 0 but had no documented pre-existing symptoms. The other 10 cases had mention of symptoms of hyperthyroidism referencing a period prior to first HPV-4 dose. This 'unmasking' phenomenon, due to health care visits that include vaccination and new workups of preexisting symptoms, may not be adequately controlled through the exclusion of Day 0 events.
authors.affiliation: Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA 91101 USA. Steven.J.Jacobsen@kp.org
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Jacobsen
authors.forename: Lina S
authors.initials: LS
authors.lastname: Sy
authors.forename: Bradley K
authors.initials: BK
authors.lastname: Ackerson
authors.forename: Chun R
authors.initials: CR
authors.lastname: Chao
authors.forename: Jeff M
authors.initials: JM
authors.lastname: Slezak
authors.forename: T Craig
authors.initials: TC
authors.lastname: Cheetham
authors.forename: Harpreet S
authors.initials: HS
authors.lastname: Takhar
authors.forename: Christine M
authors.initials: CM
authors.lastname: Velicer
authors.forename: John
authors.initials: J
authors.lastname: Hansen
authors.forename: Nicola P
authors.initials: NP
authors.lastname: Klein
mesh_terms: D000293:Adolescent; D000328:Adult; D001327:Autoimmune Diseases / Q000139:chemically induced / Q000175:diagnosis*; D002648:Child; D004341:Drug Evaluation; D064420:Drug-Related Side Effects and Adverse Reactions; D005260:Female; D006111:Graves Disease / Q000139:chemically induced / Q000175:diagnosis; D006801:Humans; D053918:Papillomavirus Vaccines / Q000009:adverse effects*; D011358:Product Surveillance, Postmarketing; D055815:Young Adult
chemical_list: D053918:Papillomavirus Vaccines