New Review Reveals Recurrent Serious Reactions to Vaccines are Rare

One reason that parents avoid vaccinating their children is out of fear of serious adverse reactions to the vaccine. Now, a new review published in the journal, Pediatrics, is revealing that if a child has a serious reaction to a vaccine, the chances of it happening again are very small.

Investigators with the Canadian Immunization Research Network, led by Gaston De Serres, MD, reviewed 29 studies—mostly on children—completed between 1982 and 2016, and “found that severe vaccine reactions (such as seizures and anaphylaxis) recurred rarely, if ever, when a child received the same vaccine again, or one with similar ingredients,” according to a press release on the review. Although common side effects, such as fevers, still recurred, they were milder in severity and did not last as long.

Cases of children and adults who experienced an allergic reaction following a vaccine were as follows: 398 patients had a history of a hypotonic hyporesponsive episode (HHE), 133 patients had anaphylaxis, and 60 had seizures.

Of those individuals who were re-vaccinated, only 5% “had another allergic response,” according to the press release. None of the individuals experienced anaphylaxis again. Study results showed specifically that, “allergic-like events recurred in 30 of 594 reimmunized patients. Fever recurred in 0% to 84% of 836 reimmunized patients, depending on the vaccine and dose number.” Of the 3 studies of children who “suffered a seizure after receiving a diphtheria, tetanus, and pertussis (DTaP) vaccine or several other routine vaccines, none had a recurrence when they were vaccinated again.”

Among the children who experienced HHEs, only 3 had a recurrent episode after the next vaccination. The risk of HHEs is most strongly associated with previous pertussis-containing vaccines; however, those used currently are thought to carry less risk.

Sean O'Leary, an infectious disease specialist at Children's Hospital Colorado who wrote an editorial on the study, shared in the press release that the results are encouraging in that they may help ease parents’ minds. More serious reactions are less likely to recur and mild reactions are typically able to be taken “in stride.” Nevertheless, Paul Offit, MD, director of the Vaccine Education Center at Children's Hospital of Philadelphia, stated in the press release that, “Vaccination is never risk-free.” However, the relatively small risks have to be weighed against the large rewards, such as protection from diseases like measles, mumps, and rubella.

Still, even if their child may not experience an adverse reaction, a mother’s friend or family member may have had a child experience a reaction, and this could influence a mother’s decision. According to a study, also published in Pediatrics, pregnant women were more likely not to have their children vaccinated on time after receiving negative information from friends and family, even if they received positive information from their doctor. This information makes learning about the true probability of adverse reactions to vaccines even more important, as well as sharing this information with families to ensure that everyone is adequately informed. Vaccines are still the #1 way to avoid being infected with some of the most debilitating illnesses in the world.