Age of measles immunization in tropics.

Maternal immunity to measles was studied in a group of 500 newborn children and another group of 500 children aged one to 12 months, before vaccination. The geometric mean titer of detectable hemagglutination-inhibition antibody was 16 for newborn children. This titer was absent in most children aged 3 to 5 months. Our previous studies indicate that from 1970 to 1972, children from the lower socio-economic classes aged 5 to 9 months were the main target of measles complications and deaths. Based on the present data, we suggest that children in developing countries should be vaccinated as young as 6 months and should be revaccinated 3 to 4 months later to assure full protection.

Stabilizing effect of magnesium chloride and sucrose on Sabin live polio vaccine.

A trivalent vaccine was stabilized with (a) 70% sucrose, (b) MgCl2 1M, and (c) 35% sucrose plus MgCl2 1/2M. A portion of each batch was kept at +4 degrees C and 22-25 degrees C. No change in titre for all 3 preparations was recorded after 9 weeks storage at +4 degrees C. While the potency of vaccines containing MgCl2 alone or mixed with sucrose and kept at +25-28 degrees C for 5 weeks was not altered, the vaccine containing only sucrose was less stable, and a drop of titre was noticed after 2 weeks of storage at +22-25 degrees C. Monovalent polio vaccines were also stabilized as above and kept at +4 degrees C or at -20 degrees C. It was found that regardless of the type of stabilizer used, 82 to 97 per cent of potency was retained after 9 months of storage at +4 degrees C or at -20 degrees C.

Improvement in the yield of oral poliovirus vaccine (Sabin strains) produced in human diploid cells.

When stationary cultures of human diploid cells in conventional Roux bottles were replaced by the development of cells in roller bottles, the yield of poliovirus, Sabin strains type 1 and 2, showed an increase of 0.5 to 1 log10. No significant difference was noticed in the yield of these viruses cultured in WI-38 and MRC-5 human diploid cells.

A model for developing countries of mass serological survey of children vaccinated against diphtheria and tetanus.

PIP: To assess the efficacy of Iran's mass immunization program, 60,000 blood samples were collected from all susceptible age groups and regions of the country. Diphtheria and tetanus antitoxin levels were determined by hemagglutination test. Official reports claim that over 70% of children in Iran receive vaccine during annual mass campaigns. At least 74% of children 3 months-7 years had diphtheria antitoxin titers sufficiently high to prevent infection, while 81-91% of those 7-13 years old were protected. Similarly, 74-82% of children 3 months-7 years had tetanus antitoxin levels high enough to avoid infection, as did 80-90% of older children. Following mass vaccination in Iran, diphtheria morbidity decreased among children but increased among adults. The incidence of tetanus has been significantly decreased in recent years due to an emphasis on immunizing girls and young mothers with adsorbed tetanus toxoid. These findings confirm both the effectiveness of Iran's vaccination campaign and the boosting effect of vaccine in older children. The hemagglutination test can be performed easily in developing countries where laboratory facilities are limited and is recommended for mass serological surveys.^ieng