The World Health Organization (WHO) recommends that the site of smallpox vaccination be examined 6-8 days after the vaccine has been administered. Development of a major reaction at the site indicates that full protection immunity has been achieved. Failure to develop a major reaction may indicate that the patient may have inadequate protection.
Major reactions indicative of immunity:
(1) response after primary vaccination
(2) response after revaccination
Major reaction indicative of immunity – after primary vaccination:
(1) At 3-4 days after the vaccination the lesion is red and pruritic.
(2) A vesicle develops with a surrounding red areola.
(3) The lesion then becomes umbilicated and then pustular by 7-11 days after vaccination.
(4) The lesion then becomes crusted and regresses over the next 7-14 weeks.
(5) After the scab falls away there is an area of permanent scarring,
Major reaction indicative of immunity – after revaccination:
(1) This may be less pronounced, evolve faster and or heal faster than after a first time vaccination.
(2) A reaction is positive if at 6-8 days after vaccination one of the following lesions is seen
(2a) a pustular lesion
(2b) an area of induration
(2c) area of congestion about a central scab or ulcer
Failure to develop an adequate reaction:
(1) immune response sufficient to suppress viral multiplication
(2) impotent vaccine
(3) poor vaccination technique
(4) allergic reaction
If an inadequate reaction is observed, then a repeat vaccination is performed by a competent person using vaccine from a fresh vial from a different lot.
If the repeat vaccination fails to elicit a major reaction, then the health care provider should contact the local or state health department or the CDC for advice.
