Long term follow-up study of a trachoma vaccine trial in villages of Northern India.

A field trial of two high titer bivalent trachoma vaccines was done in a rural area of Northern India in children under the age of 6 years. Three months later 310 of the original 451 children in the study received a booster vaccination of either of the two vaccines or a placebo. Both the sucrose gradient purified and the Genetron purified vaccine protected against trachoma infection for one year. Significant protection for two years was found only with the gradient vaccine. A 12-year follow-up study located and examined 201 subjects that had received booster vaccine. It was found that 31, 27, and 28% of the individuals in each of the three groups (two vaccine and placebo) had evidence of mostly minimally active trachoma. Additionally, from 6 to 10% of the subjects in each group had signs of mild to moderate potentially blinding sequelae. The results showed no protection by either vaccine, and there was no evidence of adverse effects from the vaccines.