July 01, 2014
2 min read

Routine vaccines rarely associated with adverse events in children

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Recent data show that some vaccines recommended for routine use in children are associated with adverse events. However, these events are rare and should be weighed against the protective benefits of vaccination, according to researchers.

Margaret A. Maglione, MPP, of the RAND Corporation in Santa Monica, Calif., and colleagues reviewed 67 studies that explored the safety of the following vaccines: DTaP, hepatitis A, hepatitis B, Haemophilus influenza type b, live-attenuated influenza, inactivated influenza, meningococcal conjugate or polysaccharide, MMR, pneumococcal conjugate or polysaccharide, rotavirus, and varicella. The review aimed to update the findings of the Institute of Medicine’s consensus report “Adverse Effects of Vaccines: Evidence and Causality,” published in 2011.

Margaret Maglione, MPP 

Margaret A. Maglione

There have been no additional studies published since 2011 that explore the association between DTaP and adverse events. As a result, the researchers support the Institute of Medicine’s conclusions on the matter, which “favors rejection” of a causal relationship between type 1 diabetes and vaccines containing diphtheria toxoid, tetanus toxoid and acellular pertussis antigens.

Results of a United States trial indicated that Hib vaccination was associated with redness (OR=2.71; 95% CI, 1.57-4.67) and swelling (OR=9.44; 95% CI, 4.9-18.19) but not with hospitalizations. A trial in Vietnam found Hib vaccine was not associated with any serious adverse events, including convulsion, diarrhea, fungal infection or gastroesophageal reflux disease.

A study that investigated possible relationships among Hib, PCV, MMR, DTaP, trivalent inactivated vaccine, hepatitis A, varicella, and meningococcal vaccines and immune thrombocytopenic purpura in children found moderate evidence of an association between hepatitis A vaccination and purpura in children aged 7 to 17 years. This association was not found among children aged 2 to 6 years.

Due to high-risk bias and low quality, a study presented insufficient evidence that hepatitis B vaccine is associated with autism.

Researchers found insufficient evidence of an association between inactivated polio virus vaccine and sensitivity to food allergens among neonates.

Large, high-quality post-licensure studies found live-attenuated influenza vaccine and trivalent inactivated vaccine were linked to mild gastrointestinal disorders, including short-term vomiting and diarrhea in children. Researchers considered this to be moderate evidence of these adverse events.

Strong evidence indicated an association between MMR vaccine and febrile seizures. Further, there was strong evidence that MMR vaccine was not associated with an increased rate of new-onset autism (OR=1.1; 95% CI, 0.64-1.9).

Regarding meningococcal vaccine, moderate evidence showed the vaccine may cause anaphylaxis in children who are allergic to ingredients. There was insufficient evidence of an association with less serious adverse events such as headache, irritability and urticarial.

A US study including more than 200,000 children found that PCV13 (Prevnar13, Pfizer) was associated with febrile seizures and that coadministration of influenza vaccine increased risk. Risk differences varied by age.

Moderate evidence showed rotavirus vaccines were associated with intussusception, but these occurrences were rare and risk factors have not been investigated.

Researchers found strong evidence of an association between varicella vaccine and complications in immunodeficient children aged 11 to 17 years.

Four high-quality epidemiologic studies evaluated the relationship between oral or injected polio vaccine, diphtheria-tetanus pertussis vaccine, MMR, Hib, and hepatitis B vaccine and onset of childhood leukemia. None of the vaccines were associated with leukemia nor an increased risk for leukemia.

Researchers noted some limitations to their review, including that the majority of studies did not investigate or identify risk factors for adverse events; and the severity of adverse events was inconsistently reported.

“Our findings may allay some patient, caregiver, and health care provider concerns. Strength of evidence is high that MMR vaccine is not associated with the onset of autism in children; this conclusion supports findings of all previous reviews on this topic. There is also high-strength evidence that MMR, DTaP, Td, Hib, and hepatitis B vaccines are not associated with childhood leukemia,” the researchers concluded.

Disclosure: The researchers report no relevant financial disclosures.