Effect of dose and age on immunization with rotavims vaccine 89-12

Rotavirus infections are a leading cause of severe diarrhea in infants. Initial evaluation of the live attenuated human rotavirus vaccine 89-12 indicated it was safe and immunogenic in infants 6-22 weeks of age at a dose of 10⁵ pfu. In this placebo-controlled, double-masked study, the safety and immunogenicity of two oral doses of either 10⁵ or 10⁶ pfu given to infants at about 4 (N = 67) or 6 months (N = 50) of age was evaluated. Overall, side effects were mild and transient and were only seen after the first dose. Few differences were found comparing doses although vomiting was only increased at the higher dose. Mild fever (> 100.4) was more common in vaccinees in both age groups compared to placebo recipients, but this was only significant for the 4-month-old group. An increase in mild diarrhea was only seen in 6-month-old vaccinees. All vaccine recipients developed rotavirus IgA antibody. Neutralizing antibody rises to the vaccine strain were detected in 73% of 4-month-old and 91% of 6-month-old vaccinees. Neutralizing antibodies to representatives of G1, G3 and G4 human serotypes ranged from 20-64% in 4 month old and 34-86% in 6 month old vaccinees. This rotavirus vaccine was generally safe and highly immunogenic, but as with other rotavirus vaccines, reactogenicity increased with age.