Questions & Answers
Smallpox - Evidence of Immunity and Vaccination - Response Interpretation
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Equivocal Reaction

  1. What is an "equivocal reaction"?
    Equivocal reactions consolidate a variety of previous terms, including accelerated, modified, vaccinoid, immediate, early, or immune reactions. Equivocal reactions are defined as all responses other than "major reactions".

    If an equivocal reaction is observed, check vaccination procedures and repeat the vaccination by using vaccine from another vial, if available. It is often difficult to determine if the reaction was blunted by immunity, insufficiently potent vaccine, or vaccination technique failure. If the repeat vaccination using different vaccine fails to elicit a major reaction, health-care providers should consult an allergist or immunologist before attempting another vaccination.