Immunization against neonatal tetanus in New Guinea. Antitoxin response of pregnant women to adjuvant and plain toxoids.

Immunization of pregnant women in New Guinea with three injections of plain toxoid had previously been shown to prevent neonatal tetanus. In the present study antitoxin levels induced by two oil-adjuvant toxoids (one injection), one AlPO(4) toxoid (two injections) and one plain toxoid (three injections) were compared with those induced by the same plain toxoid as used in the earlier study. At term there was no significant difference in the levels for the five toxoids, but those for the plain toxoids later declined rapidly. AlPO(4)-toxoid titres were significantly higher than the titres for the plain toxoids at the end of a year, but lower than the oil-adjuvant titres, which were the highest and most persistent. However, unacceptable side-effects (induced by subsequent lots of oil-adjuvant toxoids) preclude their routine use at present.The results indicate that a maternal antitoxin level at delivery of 0.01 unit/ml is protective. Aluminium-compound toxoid rapidly achieved titres that were better than this for at least a year, with minimal side-effects. Hence such toxoids are recommended for maternal immunization to prevent neonatal tetanus.