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Normal Reactions: Revaccination

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Click here to Zoom Revaccinated patient with small coalescing pustules at day 3 post vaccination
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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.

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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