1. There is strong evidence that the measles/mumps/rubella (MMR) vaccine is not linked to autism but that it is linked to a risk of febrile seizures.
2. There is moderate evidence that links the rotavirus vaccination to a risk of intussusception and the hepatitis A vaccine to purpura.
3. There is strong evidence that vaccinations are not associated with childhood leukemias.
Evidence Rating Level: 2 (Good)
Study Rundown: Immunizations have significantly reduced the incidence of infectious diseases in the United States. Despite this progress, childhood vaccination rates remain below optimal due to parental refusal and concern for potential adverse events (AEs). This meta-analysis evaluated the statistical association between vaccinations and AEs published in the scientific literature, including evidence from the 2011 Institute of Medicine (IOM) report, Adverse Effects of Vaccines. Results supported IOM findings of strong evidence that the measles/mumps/rubella (MMR) vaccine is not associated with autism, though it is associated with a risk of febrile seizures. A moderate association was found between both the live attenuated and trivalent influenza vaccine formulations and mild gastrointestinal events. In addition, there was moderate evidence to support a link between the rotavirus vaccination and intussusception, as well as the hepatitis A vaccine and purpura. Results also indicated that there is no evidence linking childhood leukemia with MMR, diphtheria/tetanus/pertussis (DTaP), tetanus/diphtheria (Td), or hepatitis B vaccines. Despite reported associations, AEs linked to vaccination were found to be rare. This study is limited in that it relied on published data with inconsistent reporting of AE severity; however, results suggested that the overall risk of serious AEs associated with vaccination is low.
Relevant Reading: Adverse Effects of Vaccines: Evidence and Causality
Study author, Dr. Courtney Gidengil, MD, MPH, talks to 2 Minute Medicine: Children’s Hospital of Boston, Instructor in Pediatrics, Department of Infectious Disease, Associate Physician Scientist at the RAND Corporation.
“Concerns about the safety of vaccines have become more widespread in recent years, leading some parents to decline recommended vaccinations for their children. We set out to update an Institute of Medicine 2011 report that examined the safety of vaccines, and expanded the review to include vaccines not covered by the report. We found no evidence that the MMR vaccine is linked to the onset of autism, a concern often cited by parents who decline to have their children immunized. We did find that some childhood vaccines are linked to rare adverse events. Some adverse events are relatively minor, such as redness and pain at the site of an injection, while others, such as febrile seizures, can be more serious. Our study adds to the substantial body of evidence showing that the benefits of vaccines clearly outweigh the low risks of serious side effects.”
In-Depth [meta-analysis]: This systematic review evaluated AEs associated with childhood vaccines. Sixty-seven studies were identified by electronic literature search and compared to data provided by the IOM 2011 report. Studies employing case studies or passive surveillance for vaccine-related AEs were excluded. Compiled evidence was then rated using the Agency for Healthcare Research and Quality (AHRQ) rating scale of high, moderate, or insufficient evidence. Findings suggested a high strength of evidence that the MMR vaccine is not associated with autism, although there was strong evidence linking the MMR vaccine to febrile seizures. In addition, moderate evidence suggested an association between the trivalent and live attenuated influenza vaccines and mild gastrointestinal complaints.This study additionally evaluated three vaccinations that were not studied by the IOM: rotavirus, hepatitis A, and haemophilus influenza B (Hib) vaccinations. Moderate evidence was found linking the rotavirus vaccines with intussusception and the hepatitis A vaccination to purpura. The Hib vaccine was not found to be associated with any serious AE. Finally, the study found a high strength of evidence that there is no link between vaccinations and childhood leukemia.
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