Saar Kuzi
Alessandra Coutinho Fernandes
William Cope
Richard Tapping
Kashif Ahmad
Reda Sadki
Shubhra Kanti Karmaker Santu
Adam P Rusch
Elizabeth Edwards
Matthew LawFA16 Immunization Module’s Updates
Adverse reactions to vaccines
An adverse reaction refers to any unfavorable effect directly caused by a vaccination. This is not to be confused with an adverse event, which instead refers to any possible medical event following a vaccination, that may or may not be directly related to the vaccine itself. An adverse event may be specifically caused by the vaccination (making it an adverse reaction) or it may be caused by some other source and its timing is simply a coincidence.
Acute adverse reactions to vaccines are categorized into three groups: local, systemic, and allergic. Local adverse reactions are the most common, occurring with about 80% of all vaccinations. Local reactions typically include mild pain, swelling, and redness (common signs of inflammation) where the vaccine is injected and usually occur within a few hours of injection. Less commonly, there can be more severe local reactions, an example of which is the Arthus reaction which is characterized by severe pain, swelling, edema, and hemorrhage 4-12 hours after injection. An Arthus reaction, associated with tetanus or diphtheria toxoids, is a local inflammation of blood vessels caused by overly high titers of antibodies forming immune complexes and subsequent activation of the complement system.
Systemic adverse reactions, more common with live attenuated vaccines, include mild, nonspecific symptoms such as fever, muscle pain, headaches, loss of appetite, and malaise. These reactions are caused by the replication of the vaccine virus, usually occurring 3-21 days after vaccination, which is the virus' incubation period.
Allergic reactions can either be caused by the vaccine antigen directly or by other components of the vaccine like the preservatives, stabilizers, or antibiotics included. Although very rare, more severe allergic reactions known as anaphylaxis can occur and they may even be deadly. Patients can be screened prior to vaccinations in order to reduce the risk of allergic reactions.
Sources:
https://www.cdc.gov/vaccines/pubs/pinkbook/downloads/genrec.pdf
http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5503a1.htm
@ Stephen Shey Proper word choice is highly important in the medical field as indicated by your distinction between adverse reaction and adverse event with regards to vaccines. Having done an update on the vaccines available for diphtheria and tetanus, I found the mention of the Arthus reaction to be very interesting. It might be important to note that the large presence of antibodies in this circumstance is due to an individual's prior sensitization to the antigen(s).
These adverse reactions to vaccination are dependent on the type of vaccine (live attenuated vs. toxoids) as well as the individuals immune system. I wonder if the same holds true for passive immunization but in this case any immune response is unwanted and our immune system may even lead to loss of benefit of the passive immunization. It may be wise to give cortisol to patients being passively immunized to avoid adverse reactions. @Stephen