Tetanus and diphtheria immunity in an elderly population in Los Angeles County.

Fifty-four per cent of 246 subjects attending senior citizen centers (mean age 69), and 29 per cent of 111 convalescent hospital subjects (mean age 82) had protective levels of tetanus antitoxin (greater than or equal to 0.01 units/ml). Age-specific immunity levels were lower for females than males, and generally decreased with age. Forty-eight and one-half per cent of the senior citizen center subjects and 55.9 per cent of the convalescent hospital subjects had protective levels of diphtheria antitoxin (greater than or equal to 0.01 units/ml).