Research Question

  1. What is the evidence that vaccines routinely given to U.S. children are safe?

BACKGROUND: Concerns about vaccine safety have led some parents to decline recommended vaccination of their children, leading to the resurgence of diseases. Reassurance of vaccine safety remains critical for population health. This study systematically reviewed the literature on the safety of routine vaccines recommended for children in the United States. METHODS: Data sources included PubMed, Advisory Committee on Immunization Practices statements, package inserts, existing reviews, manufacturer information packets, and the 2011 Institute of Medicine consensus report on vaccine safety. We augmented the Institute of Medicine report with more recent studies and increased the scope to include more vaccines. Only studies that used active surveillance and had a control mechanism were included. Formulations not used in the United States were excluded. Adverse events and patient and vaccine characteristics were abstracted. Adverse event collection and reporting was evaluated by using the McHarm scale. We were unable to pool results. Strength of evidence was rated as high, moderate, low, or insufficient. RESULTS: Of 20 478 titles identified, 67 were included. Strength of evidence was high for measles/mumps/rubella (MMR) vaccine and febrile seizures; the varicella vaccine was associated with complications in immunodeficient individuals. There is strong evidence that MMR vaccine is not associated with autism. There is moderate evidence that rotavirus vaccines are associated with intussusception. Limitations of the study include that the majority of studies did not investigate or identify risk factors for AEs; and the severity of AEs was inconsistently reported. CONCLUSIONS: We found evidence that some vaccines are associated with serious AEs; however, these events are extremely rare and must be weighed against the protective benefits that vaccines provide.

Key Findings

  • There are some risks associated with some childhood vaccinations, but overall the evidence shows that vaccines are very safe.
  • There is strong evidence that the MMR (measles, mumps, and rubella) vaccine is not associated with autism in children.
  • There is strong evidence that several common vaccines for children—MMR, DTaP (diphtheria, tetanus, and acellular pertussis), Td (tetanus-diphtheria), Hib (Haemophilus influenza type b), and hepatitis B—are not associated with childhood leukemia.
  • There is moderate evidence that vaccines against rotavirus, which causes diarrhea and dehydration in children, can increase the risk of a serious type of intestinal blockage called intussusception, but this event occurs in only 1 to 5 of 100,000 vaccinations, depending on brand.
  • The study also supports earlier findings that the MMR vaccine, pneumococcal vaccine, and influenza vaccine (particularly when given along with pneumococcal vaccine) are associated with febrile seizures in children; actual occurrence is very rare.
  • Serious side effects associated with vaccines are extremely rare and must be weighed against the substantial protective benefits of vaccines.

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