Mireya Perez

Protection against severe rotavirus diarrhoea by rhesus rotavirus vaccine in Venezuelan infants

The efficacy of the rhesus rotavirus vaccine candidate MMU-18006 was evaluated in a longitudinal double-blind field trial in Caracas, Venezuela. 247 infants aged 1-10 months were studied and followed for up to 1 year (201 completed the 1-year surveillance): 123 received a dose of 10(4) plaque-forming units of the vaccine orally and 124 received placebo. 21 episodes of rotavirus diarrhoea were detected, 16 in the controls and 5 in the vaccines: vaccine efficacy against any rotavirus diarrhoea was thus 68%. In the 1-5-month-old group the vaccine efficacy was 93%; only 1 episode of rotavirus diarrhoea was detected in 68 vaccinees and 15 such illnesses were observed in 65 controls (p less than 0.0001). For the entire study group vaccine efficacy was 100% against the most severe rotavirus diarrhoeal episodes.

Efficacy of the rhesus rotavirus-based quadrivalent vaccine in infants and young children in Venezuela.

BACKGROUND Rotaviruses are the principal known etiologic agents of severe diarrhea among infants and young children worldwide. Although a rhesus rotavirus-based quadrivalent vaccine is highly effective in preventing severe diarrhea in developed countries, in developing countries its efficacy has been less impressive. We thus conducted a catchment study in Venezuela to assess the efficacy of the vaccine against dehydrating diarrhea. METHODS In this randomized, double-blind, placebo-controlled trial, 2207 infants received three oral doses of the quadrivalent rotavirus vaccine (4x10(5) plaque-forming units per dose) or placebo at about two, three, and four months of age. During approximately 19 to 20 months of passive surveillance, episodes of gastroenteritis were evaluated at the hospital. RESULTS The vaccine was safe, although 15 percent of the vaccinated infants had febrile episodes (rectal temperature, > or =38.1 degrees C) during the six days after the first dose, as compared with 7 percent of the controls (P<0.001). However, the vaccine gave 88 percent protection against severe diarrhea caused by rotavirus and 75 percent protection against dehydration, and produced a 70 percent reduction in hospital admissions. Overall, the efficacy of the vaccine against a first episode of rotavirus diarrhea was 48 percent. Horizontal transmission of vaccine virus was demonstrated in 15 percent of the vaccine recipients and 13 percent of the placebo recipients with rotavirus-positive diarrhea. CONCLUSIONS In this study in a developing country, the quadrivalent rhesus rotavirus-based vaccine induced a high level of protection against severe diarrheal illness caused by rotavirus.

Immune response to three doses of quadrivalent rotavirus vaccine: 1-year follow-up

Twenty-eight children who received three doses of the quadrivalent rotavirus vaccine with 4 x 10(5) plaque-forming units (p.f.u.) were followed during a year after vaccination. Serum samples were obtained and evaluated for rotavirus IgA and neutralizing antibodies against vaccine and human rotavirus strains. At the end of the study, up to 61% of the children showed an increase in circulating IgA antibody levels. Nearly all of the vaccinated children increased their neutralizing antibody titres against the vaccine strains, and 25-54% against human rotavirus serotypes. After comparing the vaccinees with a population of children naturally infected with serotype G1 in the same study area, we conclude that three doses of 4 x 10(5) p.f.u. of the quadrivalent vaccine should prepare the child against future severe rotavirus diarrhea.