Childhood Vaccines: Serious Adverse Events Rare

Marcia Frellick

July 01, 2014

The benefits of routine childhood vaccines outweigh the risks of rare adverse events, according to results of a new systematic review. Although some vaccines are associated with serious adverse events, these events are extremely rare, the authors write.

The researchers conducted a literature review of the safety of vaccines routinely recommended for children aged 6 years and younger and found that the strength of evidence is high that the measles, mumps, and rubella vaccine (MMR) is not associated with the onset of autism in children, and MMR; diphtheria, tetanus, acellular pertussis vaccination (DTaP); tetanus-diphtheria (Td); Haemophilus influenza type b (Hib); and hepatitis B vaccines are not associated with childhood leukemia.

"Our findings findings may allay some patient, caregiver, and health care provider concerns," the authors conclude.

Margaret A. Maglione, MPP, from RAND Corporation, Santa Monica, California, and colleagues addressed the safety of these vaccines: DTaP, hepatitis A, hepatitis B, Hib, influenza (live attenuated and inactivated), meningococcal (conjugate or polysaccharide), MMR, pneumococcal (conjugate or polysaccharide), rotavirus, and varicella. The results of their review were published online July 1 in Pediatrics.

The Agency for Healthcare Research and Quality commissioned the review to identify any gaps in evidence regarding the safety of routinely recommended vaccines.

Concerns have led some parents to refuse the vaccines, resulting in the resurgence of diseases such as measles and pertussis.

The researchers included 67 studies in the review. Data were drawn from sources including PubMed, Advisory Committee on Immunization Practices statements, package inserts, manufacturer information packets, and the 2011 Institute of Medicine consensus report on vaccine safety.

The authors included only studies that used active surveillance and had a control mechanism. In addition, they included studies in which the strength of evidence was rated as high (further research is very unlikely to change conclusions), moderate (further research may change conclusions), low (further research is likely to change conclusions), and insufficient (evidence is unavailable or does not permit conclusions).

The strength of evidence was high for a link between MMR and febrile seizures, and the varicella vaccine was associated with complications in immunodeficient individuals. There was moderate evidence that rotavirus vaccines are associated with intussusception, but these instances were all rare. For example, although 1 large US epidemiologic study found no association, a recent analysis of the US Post-Licensure Rapid Immunization Safety Monitoring program found that both RotaTeq (Merck) and Rotarix (GlaxoSmithKline) were associated with intussusception in the short term. Estimated rates were 1.1 to 1.5 cases per 100,000 doses of RotaTeq and 5.1 cases per 100,000 doses of Rotarix.

Limitations of the literature review include that the majority of studies did not investigate or identify risk factors for adverse events, and that the severity of adverse events was inconsistently reported, the authors acknowledge.

In an accompanying editorial, Carrie Byington, MD, from the Department of Pediatrics, University of Utah, Salt Lake City, said physician confidence is critical in reassuring parents.

"Parents trust their child's doctor over government officials, family members, or celebrities as the best source of information on vaccine safety," Dr. Byington writes.

"Clinicians can examine the nonbiased data presented in the [Institute of Medicine] report and the report by Maglione et al to increase their own confidence in vaccine safety and their advocacy for vaccines. Ideally, provider confidence in vaccine safety will increase the confidence of the families they serve and increase vaccination rates for children, safeguarding the health of the nation."

The review was supported by the Agency for Healthcare Research and Quality, US Department of Health and Human Services. The authors have disclosed no relevant financial relationships. The editorial was supported by the HA and Edna Benning Presidential Endowment; National Center for Advancing Translational Sciences of the National Institutes of Health. Dr. Byington has intellectual property in and receives royalties from BioFire Diagnostics, Inc.

Pediatrics. Published online July 2, 2014.


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