Allergic Reactions To Vaccines

By Taryn Richardson, MD

Comprehensive Allergy and Asthma Care Center, LLC

More Child Health and Safety Articles

Allergic Reactions To Vaccines

It is hard to give an accurate estimate of true allergic reactions to vaccines. Research that has been done in this area varies in the design of the study and thus the results. Vaccines contain components that have the potential to cause an allergic reaction. A list of potential allergens in currently available vaccines is maintained in the Institute for Vaccine Safety website (www.vaccinesafety.edu). The most common components responsible for acute allergic reactions are egg protein and gelatin.
Influenza (seasonal and H1N1) and yellow-fever vaccines are grown on egg embryos and thus contain residual egg protein. On the contrary, the measles-mumps-rubella (MMR) vaccine is grown in chick embryo-derived fibroblast cells and do not contain any significant amount of residual egg protein. Gelatin is a component of several vaccines including the varicella, diphtheria-tetanus-acellular pertussis (DTaP), MMR, and Japanese encephalitis vaccines. Of note, one vaccine can be made by several different manufacturers therefore each manufacturers product can have differences in actual components. It is possible to have an allergic reaction to one manufacturers vaccine and not have a reaction to the same vaccine made by a different manufacturer.
There are two main types of reactions to vaccines immediate and delayed. An immediate-type reaction occurs within minutes up to a few hours after exposure to an allergen. The most common symptoms experienced with this type of reaction are hives and angioedema (swelling). Anaphylaxis can also occur. Anaphylaxis is a type of reaction that involves multiple organ systems respiratory (cough, wheeze, shortness of breath), gastrointestinal (nausea, vomiting, abdominal pain), vascular (drop in blood pressure), mucosal (swelling of the throat, obstruction of the airway, stridor) and can be life threatening. Delayed-type reactions usually occur hours to days after exposure to an allergen. The most common symptoms experienced with this type of reaction are rashes. These rashes can vary in presentation.
During the office evaluation, the initial step of an Allergy physician is to get the detailed events surrounding the reaction. This will help to determine if this was an immediate versus delayed reaction or not a reaction at all. If it is determined to be an immediate reaction, based on the particular office protocol, skin testing can be performed to the suspected components and/or the actual vaccine. Sometimes, the vaccine must be diluted and tested intradermally which means that a small amount is placed just under the skin and observed for reaction.
Based on the results of your testing, the severity/type of allergic reaction, and the need for additional vaccination, decisions about how to proceed with future vaccinations are made on a case-by-case risk/benefit basis.