Adverse Events Rare With Vaccines

Jonathan Temte MD, MS, PhD  (Expert Comment)

Polio visited me twice in the past week. On call, I admitted a patient with post-polio syndrome. Acquired at age 2 from her 9-year old sister, polio has been a constant in her life. When I asked if her children were fully immunized, I was greeted with a look of disbelief. In a recent conversation about ebola, my sister told of my parents’ enthusiasm as they gathered my older siblings to go to a public vaccination site to take advantage of the newly developed polio vaccine in the mid-1950s. I mention these incidents to highlight the effects of two generations of declining childhood infections. Due to the overwhelming success of vaccines, we have lost our fear of the diseases they prevent. The enthusiasm once centered on protecting one’s children from a long list of significant pathogens has been replaced by hesitancy about vaccine adverse effects.

Maglione and colleagues provide us with a timely and well-done systematic review of vaccine safety in US children, which should help to reduce this vaccine hesitancy. It should be first noted that this review was conducted by an independent entity—the RAND Corporation—and funded by the Agency for Healthcare Research and Quality (AHRQ), both of which are not usually involved in vaccine science. This approach disarms those who are still entrenched in the magical thinking of vaccine manufacturer conspiracies. Similar to the 2011 Institute of Medicine (IOM) consensus report “Adverse Effects of Vaccines: Evidence and Causality,” this report provides very accurate information on the harms caused by vaccines.

The authors identified over 20,000 initial papers, distilling this set to 67 studies that met inclusion criteria for a high-quality systematic review. Strength of evidence was evaluated using a standardized approach based on GRADE (Grading of Recommendations Assessment, Development and Evaluation).

Highlights include the following pairings for which there are no associations:

  • MMR and autism spectrum disorders: high-quality evidence
  • Childhood vaccines and leukemia: high-quality evidence
  • DTaP and type 1 diabetes: moderate-quality evidence
  • Hib and any serious adverse events: moderate-quality evidence

The authors also found pairings for which associations exist:

  • MMR and febrile seizures: high-quality evidence
  • Varicella and dissemination (especially with immunodeficiency): high-quality evidence
  • PCV-13 and febrile seizures: moderate-quality evidence
  • Rotavirus and intussusception: moderate-quality evidence

In general, the findings support and update the 2011 IOM report. Primary care physicians need to review this well-done systematic review, especially as misinformation on MMR and autism is still abundant in practice. There are no surprises within the reported associations; rather physicians and their patients should be reassured that known serious adverse events are extremely rare and the absolute risks are extremely low. Accordingly, these rare events must be weighed against the protective benefits provided by vaccines.  Reviewed/posted Dr. Russell

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