Antibody response to successive booster doses of tetanus toxoid in adults.

A study of the rise and fall in circulating tetanus antitoxin in a group of 15 adults after basic and booster immunization indicates that although individuals vary greatly in their responsiveness to toxoid, the falloff in antitoxin appears to be fractionally constant for each individual, and over periods of 5 to 6 years appears to be the same after successive doses. The low level of antitoxin noted in some individuals after basic immunization with a plain toxoid preparation cannot always be rectified by the use of an adsorbed toxoid as a booster. Results indicate that routine boosters need not be administered more frequently than every 10 to 20 years, provided an adsorbed toxoid has been used to initiate active immunization.