Vaccine

Successful Smallpox Vaccination (22:V1:34-35)

The usual response to a “first-time” or primary vaccination, or to a repeat vaccination after a long period of time is called a “major” response. This involves the development of a papule at the vaccination site about 3-5 days following vaccination. Approximately 7 days following primary vaccination, a vesicle (known as a “Jennerian vesicle”) surrounded by erythema forms at the site. It then evolves into a pustule by days 5-8. The peak site response occurs around days 8 to 10, and is when the greatest amount of erythema or swelling is seen. Axillary lymph nodes may also be more swollen at this time and the vaccinee may experience fever for a couple of days. The site lesion then starts to dry up to form a scab at about day 14, with separation of the scab beginning about 14-21 days after vaccination.

Vaccine sites should be examined for the expected vesicle or pustule around day 7 following vaccination to confirm the vaccination was successful. A revaccinated person often develops a skin reaction similar to that after primary vaccination, but the lesion progresses faster than after primary vaccination. (22:V6:58)

Some people do not develop a typical skin lesion after vaccination. All responses other than major reactions are referred to as equivocal. There are several possible causes of equivocal reactions. (22:V6:61) The person may be sufficiently immune to suppress viral replication. Unless the person was recently vaccinated or vaccinated multiple times in the past, they are probably not immune. The person may be allergic to a component of the vaccine, which leads to a hypersensitivity reaction at the site. An equivocal reaction could also be caused by insufficiently potent vaccine or incorrect administration technique. In general, a person who has an equivocal response to vaccination should be revaccinated using vaccine from another vial, if possible. (22:V6:61)

A revaccinated patient is considered to have had a major reaction if they produce a pustular lesion or have an induration surrounding a central crust or ulcer.

In general, alcohol, soap and water, or other chemical agents are not needed for preparation of the skin for vaccination unless the area is grossly contaminated. If needed, soap and water are the preferred cleaning agents. (22:V6:45) If any cleaning agent is used, the skin must be thoroughly dry in order to prevent inactivation of the vaccine.

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