Measles vaccine


Measles vaccine is an attenuated live virus vaccine cultured on chick embryo fibroblasts. Much controversy exists concerning its use in egg-allergic children.
 
Incidence
< 71.6/million doses (life-threatening anaphylactic reactions).
 
Risk factors
Allergic reactions to food gelatin.
 
Egg allergy: controversial
 
Clinical manifestations
Anaphylactic shock, cough, wheezing, urticaria, angioedema.
 
Non-immediate mild skin eruptions (several to 48 hours after vaccination).
 
Diagnostic methods
Cutaneous testing (controversial): patients with or without allergy may have positive skin test reactions to the vaccine and still be safely immunized.
 
Specific IgE to gelatin (immunoblotting, UniCAPâ/Pharmacia CAP System, fluorimetric ELISA).
 
Gelatin specific cell mediated immunity: in vitro lymphocyte proliferation assay, antigen specific IL 2 responsiveness (non immediate reactions to gelatin).
 
Mechanisms
IgE-mediated hypersensitivity due to the presence of minute quantities of ovalbumin (37 to 260 pg).
Neomycin: few cases (controversial).
 
Gelatins: numerous papers show a strong relationship between systemic immediate-type allergic reactions to vaccine and the presence of specific IgE to gelatins.
 
Management (controversial)
Measles vaccine containing the Edmoston-Zagreb strain (grown in human diploid cells) has lower immunogenicity than the Schwarz strain grown in a chick embryo fibroblast culture.
 
Up to now (1997), 1326 egg-allergic children who received the Schwarz strain measles vaccine suffered no allergic reactions, whereas 43 non egg-allergic children showed immediate reactions after the immunization.
 
In egg-allergic patients, some doctors perform skin prick-tests with vaccine (1/10).
  • if positive administer subcutaneously 0.05 ml at 1/100, 1/10, pure up to a total dose of 0.5 ml (at 15 minute intervals)
     
  • if negative perform an intradermal tests with measles vaccine 1/100
if positive, proceed in the same way as for a positive prick-test
 
if negative, administer the total dose of vaccine, i.e. 0.5 ml subcutaneously under medical supervision (30 minutes).

This protocol is contested by many authors who prefer the following recommendations:

  1. all immunizations should be performed by those capable of managing vaccine-associated anaphylaxis.
     
  2. egg allergy is not a contraindication to immunization with MMR. In individuals with a history of anaphylaxis to eggs, measles immunization may be routinely administered nner without prior skin testing. Immunization should be performed where adequate facilities are available to manage anaphylaxis. At-risk patients should be observed for 30 minutes.
     
  3. Measles vaccine or MMR is contraindicated in individuals with a previous anaphylactic reaction to vaccine containing measles.
     
  4. Observation for post measles-vaccine anaphylaxis should be improved, and prospective studies should be initiated to better define the risk in individuals with egg allergy.

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.