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The nature of the response to revaccination depends on the degree of residual immunity following previous vaccination.
One of the following responses will occur:
| Response |
Description |
Typical primary reaction |
Clear cut pustule 6-8 days after vaccination |
Major reaction |
Area of definite induration or congestion surrounding a central lesion that may be a scab or ulcer 6-8 days after vaccination. The evolution of the lesion is more rapid than following a primary reaction. |
Equivocal
reaction |
Any other reaction or response including:
| • |
“Allergic” reaction Erythema and a small, evanescent
papule present within several days that resolves quickly. These are “sensitivity” reactions that
can be evoked with vaccine virus that is no longer
viable. Revaccination is indicated. |
| • |
No reaction In some individuals, no take
is seen after revaccination, even at long intervals after a primary vaccination. Usually this is due to poor technique, low potency vaccine, or inactivation of the virus at the skin site (e.g. if alcohol is used to prepare the
site). Revaccination is indicated using vaccine of assured potency. |
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In general, the shorter the interval between first-time vaccination and revaccination, the more likely it is that there will be no “take” or major reaction. Evaluation of the vaccination site on days 6-8 will minimize the risk of missing or misclassifying the "take."
Among those for whom 25 years or more has elapsed since last vaccination, essentially all should experience a "major reaction".
If a patient has never had a successful take, the patient should be informed that he/she is almost certainly
not immune.
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