The effect of diarrhea on oral poliovirus vaccine failure in Brazil.

The effect of diarrhea on oral poliovirus vaccine (OPV) failure was evaluated using data from Brazil, where 728 infants were immunized at birth (OPV1) and approximately 6 (OPV2), 10 (OPV3), and 14 (OPV4) weeks. Recent diarrhea history was significantly associated with increased vaccine failure only after OPV2 for poliovirus types 2 and 3. In multivariate models, controlling for breast feeding, season of vaccine administration (type 3 only), maternal antibody (type 3 only), and immunization campaign exposure (type 3 only) strengthened this effect. Diarrhea at OPV receipt was associated with vaccine failure to poliovirus types 1 and 3 only after OPV2. These data support the current recommendation that children with diarrhea receive OPV and be reimmunized once their illness resolves. Expanding this recommendation to include children with a recent diarrhea history should be considered. While the effect of diarrhea on vaccine failure may be limited to OPV2, programmatic realities may preclude dose-specific recommendations.

Class-specific antibody responses in school children vaccinated with an A/Brazil/11/78 (H1N1)-like recombinant influenza virus prepared from the A/Leningrad/134/57 paediatric cold-adapted donor strain.

Forty-three school children from 8 to 11 years old were vaccinated intranasally with two doses of a paediatric attenuated influenza vaccine developed by reassortment between cold-adapted A/Leningrad/134/57(H2N2) and an A/Brazil/11/78(H1N1)-like strain. Two vaccine doses were administered 1 month apart in a randomized, blind, placebo-controlled study. Although the first vaccine dose had a low infectivity titre, overall 65% of children who received two doses of vaccine showed serological evidence of infection by HI tests. Serum IgA antibody responses against the vaccine strain were detected in nearly 50% of the vaccines and serum IgG antibody responses were detected in approximately equal to 40% by an enzyme immunoassay.

Randomised trial of alternative formulations of oral poliovaccine in Brazil.

In February to July, 1986, an outbreak of type 3 poliomyelitis occurred in north-east Brazil that was linked to type-specific failure of trivalent oral polio vaccine (TOPV). To see if alternative vaccines would improve seroconversion to type 3, 441 children less than 5 years of age who had previously received no or up to four doses of TOPV were randomly assigned to receive one dose of standard TOPV (1,000,000, 100,000, and 300,000 median tissue culture infection doses [TCID50] of types 1, 2, and 3, respectively); a new formulation of TOPV containing twice the dosage of type 3 (600,000 TCID50); or a monovalent vaccine containing 300,000 TCID50 of type 3. While rates of seroconversion to types 1 or 2 were equivalent following vaccination with either formulation of TOPV, children who received the new formulation were 2.7 times more likely to seroconvert to type 3. Similar differences for type 3 were observed when monovalent vaccine was compared with standard TOPV, though both groups had received the same dose of type 3 antigen. The low rate of seroconversion to type 3 in the standard TOPV group was associated with a higher rate of reinfection with type 2, which also appeared to interfere to some extent with seroconversion to type 1. These findings extend earlier observations that interference from Sabin type 2 virus may be an important contributory cause of type-specific TOPV failure, and suggest that interference can be overcome with alterations in the formulation.