Controlled field trials with oral and nasal immunization against tetanus in humans.

Under field conditions, the comparative effectiveness of oral, nasal and intramuscular vaccination of humans with tetanus toxoid was investigated. The effectiveness was tested by the determination of antitoxin titers with the L+-method. Oral booster vaccination produced only very low and irregular increases in antitoxin titer even at the highest dose of 6,000 Lf toxoid. In the most favourable case following triple oral immunization, a rise from 6.2 to 6.6 I.U. was achieved. Primary oral vaccination failed to stimulate measurable antitoxin production. After nasal booster vaccination with 1,000 Lf toxoid, a ten-fold rise in antitoxin titer was detectable. Following primary nasal vaccination, an average neutralization titer of 1 I.U. was achieved. The results of intramuscular and nasal booster vaccinations were similar although the antitoxin titers were significantly higher after primary intramuscular vaccination than after primary nasal vaccination. The average antitoxin titer amounted to 11.6 I.U. These results indicate that primary and booster vaccination against tetanus by the nasal route is a safe and effective procedure.