Vaccine Reactions

Any time a person takes a medication, even a preventative one such as a vaccine, they can have an adverse reaction. Vaccines are made to activate the immune system and help the immune system become familiar and form protection against a potential threat. Because vaccines activate the immune system, mild reactions are common. 

Sometimes a person can have allergic reactions to ingredients of the vaccine. These allergic reactions can be to the active ingredients but are more often to the inactive ingredients (excipients) used to stabilize or produce the vaccine. These allergic reactions can range from mild to severe, including a life-threatening allergic reaction called anaphylaxis. 

Sometimes mild reactions resolve without treatment or may improve with antihistamines like diphenhydramine. 

Anaphylaxis has some of the same symptoms of mild allergic reactions, but the symptoms are more severe and occur in more than one system. Symptoms of anaphylaxis occur abruptly and require emergency medical treatment. They do not resolve on their own.

Vaccine-related Reactions

How common is anaphylaxis to vaccines?
Anaphylaxis to vaccines is historically rare. The Center for Disease Control and Prevention (CDC) reporting system has identified that they occur with about one in every million doses for most vaccines. Emerging data suggest these reactions may occur 5 times more often in the mRNA vaccines against COVID-19 (see Do the COVID-19 vaccines cause anaphylaxis?).

What is the role of the allergist in vaccine reactions?
An allergist can determine whether it is safe for your child to get a vaccine if they have a history of concerning allergies to vaccines or excipients or evaluate your child after they have had an allergic reaction to a vaccine.

How are vaccines assessed for safety?
Vaccine safety in the US is the responsibility of the CDC and Food and Drug Administration (FDA). Detailed procedures are in place for reporting and following up of reports of adverse reactions to vaccines. Reactions to vaccines that are suspected to be allergic reactions are reported to the through a Vaccine Adverse Events Reporting System (VAERS). The CDC safety officers and allergy consultants review the report to determine the likelihood of the reaction qualifying as anaphylaxis. The director of our Drug Allergy Program, Kimberly A. Risma, MD, PhD, has served as an allergist consultant for the allergic reactions to COVID-19 mRNA vaccines. 

Cincinnati Children's participated in the COVID-19 vaccine trials.