Characteristics
Beginning in the early 1900s, prophylaxis was attempted
with toxin–antitoxin mixtures. Toxoid was developed around
1921 but was not widely used until the early 1930s. It was
incorporated with tetanus toxoid and pertussis vaccine and
became routinely used in the 1940s.
Diphtheria toxoid is produced by growing toxigenic
C. diphtheriae in liquid medium. The filtrate is incubated
with formaldehyde to convert toxin to toxoid and is then
adsorbed onto an aluminum salt.
Single-antigen diphtheria toxoid is not available. Diphtheria
toxoid is combined with tetanus toxoid as pediatric
diphtheria-tetanus toxoid (DT) or adult tetanus-diphtheria
(Td), and with both tetanus toxoid and acellular pertussis
vaccine as DTaP and Tdap. Diphtheria toxoid is also
available as combined DTaP-HepB-IPV (Pediarix) and
DTaP-IPV/Hib (Pentacel)—see Pertussis chapter for more
information. Pediatric formulations (DT and DTaP) contain
a similar amount of tetanus toxoid as adult Td, but contain
3 to 4 times as much diphtheria toxoid. Children younger
than 7 years of age should receive either DTaP or pediatric
DT. Persons 7 years of age or older should receive the adult