Thank you for your inquiry.
Unfortunately, there is no definitive answer to your question, and the issue of duration of venom immunotherapy is not dealt with as specifically for different clinical scenarios related to the sting as posed in your inquiry. We simply do not have sufficient data for different clinical manifestations to be able to give statistically verified, evidence-based responses. Therefore the duration of immunotherapy is in many instances left to the discretion of the physician and the patient. In my opinion, the question is best dealt with via the Joint Task Force Parameters. For your convenience, I have copied below a couple of the salient sections taken from these Parameters. At the end of the sections is the reference and a link to this reference. Dr. David Golden is the first author. The nuances of the suggested duration of therapy is discussed in more detail in the reference itself, but the sections I have copied should give you insight, as best we can, into this issue.
Thank you again for your inquiry and we hope this response is helpful to you.
Once initiated, VIT should usually be continued for at least 3 to 5 years.42,43 An increasing body of evidence suggests that despite the persistence of a positive skin test response, 80% to 90% of patients will not have a systemic reaction to an insect sting if VIT is stopped after 3 to 5 years.44-52 There are no specific tests to distinguish which patients will relapse after stopping VIT, but there is a higher risk in some patients than others. Relapse is less likely with 5 years than with 3 years of VIT.50,53 Although most patients can safely discontinue immunotherapy after this period of time, some patients with a history of severe anaphylaxis with shock or loss of consciousness still might be at continued risk for a systemic reaction if VIT is stopped, even after 5 years of immunotherapy.46,47,52
For this reason, some experts recommend an extended duration of immunotherapy, possibly indefinitely, in such patients. Other criteria suggested for stopping VIT include a decrease in serum venom-specific IgE to insignificant levels or conversion to a negative skin test response.54 Some patients have relapsed despite negative venom skin test responses. Repeat skin (or venomspecific IgE serum) testing is not required for consideration of discontinuing VIT. Measurements of venom-specific IgG antibodies have no predictive value when discontinuing VIT. The decision on stopping VIT requires a context-sensitive flexibility based on the available evidence.
Box 11: Consider stopping VIT after 3 to 5 years
Guidelines for discontinuation of VIT are evolving. Whereas the package insert for the Hymenoptera venom extract recommends that VIT be continued indefinitely, treatment for a finite length of time (3-5 years), a decrease in serum venom-specific IgE to insignificant levels, or conversion to a negative skin test response have been used as criteria for discontinuing treatment.
When both skin and in vitro test results are negative, VIT has been discontinued with no severe reactions to subsequent stings. An increasing body of evidence suggests that despite the persistence of a positive skin test response, approximately 90% of patients will not have a systemic reaction to an insect sting if VIT is stopped after 3 to 5 years and that any reaction to a future sting is usually less severe than the reaction before VIT. It is therefore reasonable to consider discontinuation in most patients after therapy of this duration, except in certain high-risk patients described in the text. However, there always remains a small risk that future systemic sting reactions could occur. In addition, severe reactions have occurred several years after stopping VIT in a small number of patients whose skin test responses became negative while receiving VIT (although most still had positive in vitro test results).
Conversely, although some patients will lose their skin reactivity to stinging insect venom, the persistence of such reactivity does not mean that all such patients are at increased risk of having a systemic reaction if subsequently stung. There are no specific tests to distinguish which patients will relapse after stopping VIT, but there is a higher risk in some patients than in others. A decision about the duration of VIT is made individually after discussion between the patient and physician and might involve consideration of lifestyle, occupation, coexistent disease, medications, severity of sting reactions, and other factors. Repeat skin (or venom-specific IgE serum) testing is not required for consideration of discontinuing VIT. Patients with a history of severe anaphylaxis (severe airway obstruction, shock, or loss of consciousness), still might be at continued risk for a systemic reaction if VIT is stopped even after 5 years of treatment. For this reason, some recommend that immunotherapy be continued indefinitely in such patients (see text for details).
J Allergy Clin Immunol
Volume 127, Number 4
Phil Lieberman, M.D.