Thank you for your inquiry.
Unfortunately there is no definitive answer to your question. You would probably obtain different responses from different experts. A great deal depends upon your confidence in treating an event that might occur if you “push through,” the severity and nature of her reaction, how great the need is for the vaccine you are pursuing, and whether you feel you could give the dose prior to her reaction on another day or a few days (thus giving her the cumulative dose that she needs over several days).
In most instances, in cases where I have encountered a reaction, I will not “push through” on the same day. I will bring the patient back the next day and give the dose that was safely given prior to the reaction, and continue to do this until the cumulative dose reaches the desirable dose. For example, if you were doing so with tetanus toxoid, and the reaction occurred at 0.2 cc, I would bring the patient back in three subsequent days and give the patient 0.1 cc on each occasion. Thus a total of 0.5 cc could be given without further risk However if the reaction was mild you could attempt to "push through" if the patient/parent were willing. There is no consensus and the decision to do so is a "judgment call".
Parenthetically, I see no problem with your suggested protocol for desensitization, but you might want to use a published protocol. For your convenience the two references below contain such a protocol. Although they were done with the presumption that the allergy was to egg protein within the vaccine, the principles employed and schedule would apply to gelatin.
Finally my preference would be to desensitize to MMR alone. I would use separate injections.
Pediatrics Vol. 91 No. 4 April 1, 1993
Ann Allergy. 1994 Jan;72(1):25-8.
Measles, mumps, rubella vaccine administration in egg-sensitive children: systemic reactions during vaccine desensitization.
Trotter AC, Stone BD, Laszlo DJ, Georgitis JW.
Department of Pediatrics, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC.
In egg-sensitive children, measles-mumps-rubella (MMR) vaccination may cause acute allergic reactions; therefore, current recommendations are to perform skin testing with the commercial vaccine before administration to egg-allergic children. In children with positive skin tests, desensitization with the measles-mumps-rubella vaccine should be done in order to administer a full dose of the vaccine. Twelve egg-allergic children, aged 12 months to 5 years of age, were referred to our pediatric allergy clinic for MMR administration over a 20-month period. Three children had positive skin prick or intradermal tests to the MMR vaccine. Two of these three patients experienced systemic hypersensitivity reactions while undergoing desensitization to the MMR. All reactions occurred with injections of the undiluted vaccine. Based upon this experience, we recommend that egg-allergic children should continue to have cutaneous tests done to the MMR vaccine and careful observation during desensitization in those children with positive skin tests
Thank you again for your inquiry and we hope this response is helpful to you.
Phil Lieberman, M.D.