Serious adverse events resulting from vaccines routinely used in the United States are rare, according to a report funded by the Agency for Healthcare Research and Quality (AHRQ). The report, highlighted in the July issue of Pediatrics, provides the most comprehensive review to date of published studies on the safety of routine vaccines.
"The use of vaccines ranks among the most significant public health achievements," said AHRQ Director Richard Kronick, Ph.D. "This review of the evidence provides important reassurances about the safety of commonly used vaccines."
"Vaccines are some of the safest medical products available, and our recommendations and use of them is based on an assessment of the benefits and the risks," said National Vaccine Program Office Director Bruce Gellin, M.D. "This independent report reaffirmed that while serious adverse events can occur, they are rare."
The report found scientific evidence that addresses several common concerns about a variety of vaccines. For example, the report found strong scientific evidence that:
There is not a link between measles, mumps and rubella (MMR) vaccines and autism.
There is not a link between pneumonia and influenza vaccines and cardiovascular or cerebrovascular events in the elderly.
There is not a link between MMR; diphtheria, tetanus, and pertussis (DTaP); tetanus and diphtheria (Td); Haemophilus influenzae type b (Hib); and Hepatitis B vaccines and childhood leukemia.
In addition, the report found that there is moderately strong scientific evidence that:
There is not a link between human papillomavirus (HPV) vaccines and appendicitis, stroke, seizures, venous thromboembolism, onset of juvenile arthritis or onset of type 1 diabetes.
There is not a link between inactivated influenza vaccines and adverse pregnancy outcomes (such as miscarriage, low birth weight, and premature birth) for women who receive the vaccine while pregnant.
The AHRQ evidence review was conducted by the Southern California Evidence-Based Practice Center based at the RAND Corporation. The conclusion—the risk of rare adverse events must be weighed against the protective benefits that vaccines provide—is consistent with a 2011 report published by the Institute of Medicine (IOM) titled, "Adverse Effects of Vaccines: Evidence and Causality."
Some extremely rare adverse events were identified. For instance, there was evidence supporting a link between the 2009 H1N1 influenza vaccine and Guillain-Barré Syndrome in adults; however, the rate was very low, resulting in an additional 1.6 cases of the syndrome per million vaccinated.
In some instances, delaying vaccination or failure to vaccinate has contributed to outbreaks of vaccine-preventable diseases such as measles and pertussis. For example, a recent measles outbreak in Ohio was found to be caused by unvaccinated Americans who traveled to the Philippines. Partially as a result of low measles vaccination rates, the Centers for Disease Control and Prevention reported that measles cases in the United States reached a 20-year high in May 2014.
The AHRQ report is based on a scientific review of the evidence that included the results of the 2011 IOM report, plus 166 studies published after the IOM report was developed. The results from the report support findings of the 2011 IOM report and build on it by reviewing additional vaccines such as pneumococcal, rotavirus, Haemophilus influenzae type b, inactivated poliovirus and zoster.