Program Schedule

Evaluation of syncope and related events following vaccination with quadrivalent human papillomavirus vaccine (2006-2013)

Session: Poster Abstract Session: Vaccines: HPV
Friday, October 10, 2014
Room: The Pennsylvania Convention Center: IDExpo Hall BC
  • lievano_183838-7485_IDSA_Poster_FINAL.pdf (590.7 kB)
  • Background: Since licensure of quadrivalent human papillomavirus vaccine (qHPV) in 2006, several large studies have confirmed the favorable benefit- risk of qHPV. Syncope has been seen following qHPV. In some instances the paroxysmal loss of consciousness caused by cerebral hypoperfusion occurring with vasovagal syncope may be associated with seizure-like movements; health care providers (HCPs) may misinterpret these syncopal events as convulsions.  The objective of this analysis is to characterize spontaneous, postmarketing reports of convulsion and syncope after qHPV.

    Methods: Case characteristics, including time to onset, patient age, and clinical course were analyzed.  All case reports of convulsion were medically evaluated and classified as follows: probable syncope; convulsion in an individual with a history of seizures; new onset of convulsion; a diagnosis inconsistent with syncope or convulsion; or insufficient data. Reporting rates were calculated for syncope and convulsion (total number of case reports divided by the number of vaccine doses distributed).

    Results: The reporting rate for syncope was 3.9/100,000 doses distributed worldwide. The majority (72%) of syncope cases was reported in vaccinees 10-18 years of age and 88% occurred on the day of vaccination. The reporting rate for convulsion was 0.95/100,000 doses. Medical review revealed 44% are likely cases of convulsive syncope (fainting with myoclonic jerks); 6% are post vaccination seizure in patients with pre-existing seizure disorders; 6% involve diagnoses other than syncope or seizure; and ~22% could represent cases of new onset seizure. The remaining 21% are not evaluable due to lack of data. New onset cases and cases in individuals with a history of convulsion occurred at a rate of 0.27/100,000 doses.

    Conclusion: Syncope has been reported following qHPV vaccination at a low rate. HCPs should be aware of the potential and take precautions. Reported cases of convulsion post vaccination have been clinically reviewed. Many are more consistent with convulsive syncope rather than convulsion. Misinterpreting a vasovagal episode may result in unnecessary treatment; careful clinical assessment is recommended.

    Fabio Lievano, MD, Clinical Safety and Risk Management, Merck & Co., Inc., North Wales, PA, Mary Ann Goss, MSN/RN, Clinical Safety and Risk Managment, Merck and Co., North Wales, PA and Adrian Dana, MD, Clinical Safety and Risk Management, Merck Research Laboratories, Merck & Co., Inc., North Wales, PA


    F. Lievano, Merck and Co.: Employee, Salary

    M. A. Goss, Merck and Co: Employee, Salary

    A. Dana, None

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