The nature of
the response to revaccination depends on the degree of residual
immunity following the previous vaccination.
One of the following responses will occur:
Response
Description
Typical
primary reaction
Clear
cut pustule 6-8 days after vaccination
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 the first week that resolves quickly. These are
“sensitivity” reactions and do not necessarily
imply immunity. 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 primary vaccination
and revaccination, the more likely it is that there will be
no take or a major reaction.
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.
