Immune response to diphtheria booster vaccine in the Baltic states

A study was done to measure baseline levels of immunity to diphtheria and a ntibody responses to different doses of diphtheria vaccine in study partici pants in the three Baltic states, Diphtheria booster vaccines containing ei ther 3 (Estonia and Lithuania), 6 (Latvia), or 12 (Latvia) limit of floccul ation units of diphtheria toroid were administered to 2315 adults. Diphther ia antibody levels were tested before and 1-2 months after vaccination. Bef ore vaccination, 40% of the participants in Estonia, 32% in Lithuania, and 38% in Latvia had antibody levels <0.01 IU/mL, the level for minimum protec tion. After vaccination, 79% of the participants in Estonia, 83% in Lithuan ia, and 81% in Latvia had antibody levels >0.1 IU/mL, the minimum level for full protection. However, in each of the countries, about one-third of the 40- to 49-year-old participants would have benefited from additional doses of vaccine, There was not a significantly different antibody response amon g persons receiving the three different doses. Age and the level of prevacc ination immunity had a modifying effect on the response to vaccination; how ever, sex did not.