Prospective study of diarrheal diseases in Venezuelan children to evaluate the efficacy of rhesus rotavirus vaccine

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Abstract
The efficacy of a rhesus rotavirus vaccine (MMU 18006, serotype 3) against infantile diarrhea was evaluated by active home surveillance of a group of 320 children 1–10 months of age in Caracas, Venezuela. During a 1 year period following oral administration of vaccine or placebo under a double‐masked code, over 600 diarrheal episodes were detected. Etiologic studies revealed that heat‐stable toxin (ST) producing enterotoxigenic E. coli (ETEC) was the most common diarrheal agent detected (34%) followed by enteropathogenic E. coli (EPEC, 10.9%), heat‐labile toxin (LT) producing ETEC (7.6%), rotavirus (6.9%), Cryptosporidium (4.8%) and Campylobacter (1.3%). ST‐producing ETEC were also recovered from over 20% of control stool specimens obtained during diarrhea‐free periods, whereas EPEC, rotavirus, Cryptosporidium, and Campylobacter were rarely detected in such control specimens. Rotavirus was responsible for about one‐half of the more severe cases of diarrhea. Twenty‐two of 151 infants who received placebo (14.6%) and eight of 151 receiving a 104 PFU dose of vaccine (5.3%) had rotavirus diarrhea during the follow‐up period for an efficacy level of 64% against any rotavirus diarrhea. However, vaccine efficacy reached 90% against the more severe cases of rotavirus diarrhea and was notably high in the 1–4 month age group. Serotypic analysis of the rotaviruses detected suggests that the resistance induced by the vaccine was type specific since significant protection was only evident against serotype 3 rotaviruses. A 103 PFU dose tested initially in 18 children did not appear to protect against rotavirus diarrhea.