Efficacy of minimal doses of an American hepatitis B vaccine in neonates.

Eight neonates and three young children at risk for hepatitis B infection were vaccinated with minimal doses of inactivated hepatitis B vaccine. The purpose of the study was to evaluate the efficacy of low doses with a view toward reducing the cost of immunization and therefore extending the practice to a larger number of subjects and minimizing the incidence of adverse reactions to the vaccine. The patients received two intramuscular injections (0.1 ml) of vaccine at a two-month interval and a booster six months after the first dose. Anti-HBs titers were determined simultaneously by radioimmunoassay on all serum samples collected. Five of the 11 patients achieved presumably protective (greater than 10 mU/ml) antibody levels within six months after the first dose (titers between 10 and 74 mU/ml), and all but one patient achieved titers between 27 and 2,500 mU/ml within two months after the booster. No adverse reaction was observed.

Rapid detection of respiratory syncytial virus in nasopharyngeal secretions by immunofluorescence and ELISA does not justify discontinuation of virus isolation.

Direct fluorescent antibody assay (DFA) using monoclonal antibody and enzyme-linked immunosorbent assay (ELISA) for rapid detection of Respiratory Syncytial Virus (RSV) in nasopharyngeal secretions (NPS) were compared with conventional virus isolation and identification procedures in cell cultures. When 134 NPS were examined from infants and young children with acute respiratory tract infection, 42 (31%) were culture-positive for RSV and 31 of these were detected by the appearance of a typical cytopathic effect and identified by DFA either before or after its appearance, whereas 11 were identified as RSV-positive by DFA performed blindly on HEp-2 cell cultures 5 or 10 days after inoculation. DFA for RSV on NPS smears was positive in 33 (26%) cases, from seven of which RSV was not isolated. The same group of 134 NPS was tested for RSV detection by three commercial ELISA kits. The sensitivities of the three ELISA kits when compared with a combination of culture and DFA results, were comparable (53%, 51%, and 47% for Ortho, Kallested, and Abbott, respectively), whereas specificity was 100% for all three assays. In the group of 26 NPS detected as positive by both virus isolation and DFA, 20-22 (77-85% according to different kits) were found positive for RSV by the three ELISA assays. These data suggest that virus isolation is still critical for diagnosis of a fair number of cases of RSV infection. Of the two rapid techniques, DFA is a valuable complementary method, whereas ELISA still lacks sensitivity. However, both DFA and ELISA were able to detect RSV in 7 of 8 young patients with severe respiratory infection (pneumonia, bronchiolitis), thus permitting diagnosis of RSV infection at least two days before culturing.

RIA evaluation of antibody levels in neonates from HBsAg-positive mothers after active, passive, and combined immunoprophylaxis.

We evaluated the anti-HBs titers in 20 babies born to HBsAg-positive mothers and receiving different programs designed to prevent hepatitis B. Passive prophylaxis by HBIG for 6 months assured detectable antibody levels in the same period. 3 months after the last injection we could detect antibodies in 5 out of 9 cases. In no case could we detect antibodies 6 months after the last dose. Active prophylaxis by hepatitis B vaccine was able to raise anti-HBs response in 8 out of 12 babies after two or three very small doses (1.25 micrograms of antigen). 2 of these babies were given the first dose at birth. Small doses of vaccine were immunogenic in the presence of passive antibodies.