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Methods for addressing "innocent bystanders" when evaluating safety of concomitant vaccines

Shirley V Wang1, Abdurrahman Abdurrob1, Julia Spoendlin1

  • 1Division of Pharmacoepidemiology and Pharmacoeconomics, Brigham and Women's Hospital; Department of Medicine, Harvard Medical School, Boston, MA, USA.

Pharmacoepidemiology and Drug Safety
|February 15, 2018
PubMed

Insights

Investigating childhood immunization safety, this study developed a method to assess risks of vaccines given on the same day. Adjusting for age, it found little evidence of increased seizure risk from DTaP and MMR vaccines administered together.

Area of Science:

  • Immunization Safety
  • Vaccine Epidemiology
  • Pediatric Public Health

Background:

  • Childhood immunization schedules often involve multiple vaccines per visit.
  • Concerns exist regarding the safety of administering vaccines concomitantly (on the same day).
  • Observational studies face methodological challenges in assessing concomitant vaccine safety.

Purpose of the Study:

  • To address methodological challenges in observational studies of concomitant vaccine safety.
  • To develop a process for identifying specific vaccines responsible for adverse events when administered together.
  • To adjust for confounding factors related to vaccine combinations and risk factors.

Main Methods:

  • Utilized a self-controlled design for observational vaccine safety studies.
  • Proposed a method to distinguish individual vaccine contributions to adverse events.
  • Re-examined seizure risk post-measles-mumps-rubella (MMR) vaccination, assessing other vaccine effects.
  • Adjusted for time-invariant effect modifiers like age at vaccination.

Main Results:

  • Initial analyses suggested DTaP had independent and potentiating effects on seizure risk.
  • After adjusting for age and vaccine combinations, minimal evidence supported increased seizure risk with same-day DTaP and MMR administration (IRR 1.2 [0.9-1.6]).

Conclusions:

  • Adjusting for time-invariant effect modifiers, such as age, is crucial in self-controlled designs for concomitant vaccine safety.
  • Age at vaccination is structurally related to vaccination patterns in recommended schedules.
  • The findings highlight the importance of robust statistical methods in vaccine safety research.
Abstract

Keywords:
immunization schedulemethodsseizureself-controlledvaccine safety

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