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Studies on Trachoma
V. Clinical Observations in a Field Trial of Bivalent Trachoma Vaccine at Three Dosage Levels in Saudi Arabia
Summary
- 1.Bivalent trachoma vaccines, inactivated with formalin, were given to 2,117 children in a controlled study in the Eastern Province of Saudi Arabia. Three dosage levels were employed. Subjects were recalled for examination at 6 month intervals for up to 2 years.
- 2.The smallest amount of trachoma antigens, 0.25 arbitrary vaccine units, emulsified in adjuvant and given as a single injection, produced no observable effect on attack rates of clinical trachoma. The intermediate amount, an aqueous vaccine administered in 2 primary injections containing a total of approximately 0.4 arbitrary vaccine units, was followed by a lower attack rate in vaccinees than in controls, the difference being statistically significant at the 6 month examination. Six months later, although there continued to be less active trachoma in test than in control groups, statistical significance was lacking whether the vaccinees received boosters or not.
- 3.The largest amount of trachoma antigen, an aqueous vaccine containing 4.0 arbitrary vaccine units in 2 primary injections, was followed by a higher attack rate in the test group than in the controls at the end of 6 months; thereafter differences in attack rate diminished progressively to values less than those required for statistical significance.