Diseases Home > Understanding the Effects of Tdap and How It Is Given

How Does Tdap Work?

Tdap contains pertussis antigens, diphtheria toxoid, and tetanus toxoid. Toxoids are bacterial toxins that have been detoxified. Although the toxoids will not cause the actual disease, they stimulate the immune system to produce antibodies to the toxin.
"Antigen" is the generic term for substances that cause the body to produce an immune response and to produce antibodies. Tdap contains a few different pertussis antigens which have been detoxified. Much like the toxoids, the detoxified antigens will not cause the actual disease but can stimulate an immune response.
Basically, the antigens and toxoids in Tdap "trick" the body into thinking it has been exposed to diphtheria, tetanus, and pertussis. The body produces antibodies that will help fight these diseases if future exposure occurs.

When and How to Get the Vaccine

Some general considerations include the following:
  • This vaccine is given as an injection into the deltoid muscle of the upper arm (where most immunizations are given). Most people need just one dose of Tdap, except pregnant women, who need a dose during each pregnancy.
  • Your healthcare provider should shake the vial well before injecting Tdap.
  • Multiple doses of this vaccine are not recommended in most situations. After an individual receives the Tdap vaccine, all future boosters should be given as the Td (tetanus and diphtheria) vaccine.
  • In general, the vaccine should be given only if at least five years have passed since the last DTaP or Td vaccine was given. In some cases, the vaccine can be given sooner.

Dosing Information

There is only one standard recommended dosage for this vaccine. However, because there are several different similar vaccines that are given during childhood and adolescence, it can be confusing to know when exactly (or even if) this vaccine should be given.
(Click Tdap Dosage for more information.)
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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