NEUTRALIZING ANTIBODIES IN 6-YEAR-OLD CHILDREN AFTER 5 DOSES OF TETANUS TOXOID

It has recently been suggested that multiple boosters of tetanus toxoi d may enhance serum antitoxin titres but may not necessarily lead to a n effective immune response. Tetanus antitoxin titres by haemagglutina tion inhibition and mouse toxin neutralization tests were determined i n sera of 64 children, 5 and 6 years old. Primary vaccination against tetanus was given as four doses of diphtheria-pertussis-tetanus (DPT) vaccine beginning in the second or third month of life, and a booster dose given to schoolchildren at 6 years of age. In our area more than 90% of children receive five doses of tetanus toxoid before their seve nth birthday. The children were given 0.5 ml of DPT or DT containing 1 0 Lf ml-1 tetanus toxoid at each injection. The haemagglutination titr es and the toxin neutralization titres were much higher in 6-year-old than in 5-year-old children. We concluded that the fifth dose is an ef fective booster in 6-year-old children.