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BULLETIN OF THE PAN AMERICAN HEALTH ORGANIZATION. 1984; 18(2):188-92.Outbreaks of yellow fever in recent years in the Americas have prompted concern about the possible urbanization of jungle fever. Vaccination, using the 17D strain of yellow fever virus, provides an effective, practical method of large scale protection against the disease. Because yellow fever can reappear in certain areas after a 2-year dormancy period, some countries maintain routine vaccination programs in areas where jungle yellow fever is endemic. The size of the endemic area (approximately half of South America), transportation and communication difficulties, and the inability to ensure a reliable cold chain are problems facing these programs. In addition, the problem of reaching dispersed and isolated populations has been addressed by the use of mobile teams, radio monitoring, and educational methods. During yellow fever outbreaks, many countries institute massive vaccination campaigns, targeted at temporary workers and migrants. Because epidemics in South America may involve extensive areas, these campaigns may not effectively address the problem. The ped-o-jet injector method, used in Brazil and Colombia, should be used in outbreak situations, as it is effective for large-scale vaccination. Vaccine by needle, suggested for maintenance programs, should be administered to those above 1 year of age. An efficient monitoring method to avoid revaccination, and to assess immunity, should be developed. The 17D strain produces seroconversion in 95% of recipients, and most is prepared in Brazil and Colombia. But, problems with storage methods, instability in seed lots, and difficulties in large-scale production were identified in 1981 by the Pan American Health Organization and WHO. The group recommended modernization of current production techniques and further research to develop a vaccine that could be produced in cell cultures. Brazil and Colombia have acted on these recommendations, modernizing vaccine production and researching thermostabilizing media for yellow fever vaccine.
BULLETIN OF THE WORLD HEALTH ORGANIZATION. 1985; 63(2):241-8.The WHO memorandum outlines the present situation regarding pertussis vaccines, discusses ways to evaluate candidate vaccines, and identifies future research needs. Most existing whooping cough vaccines are whole-cell vaccines, combined with diphtheria and tetanus toxoid adsorbed on an aluminum or calcium carrier. As whole bacterial cells, they contain a complex array of at least 7 toxins and antigens, and display a narrow margin between potency and toxicity. The Japanese introduced an acellular vaccine, admittedly sometimes less potent, called the Precipitated Purified Pertussis Vaccine, in 1981. This material contains far less bacterial mass, notably less endotoxin, and consequently produces less fever, erythema and induration. WHO has not yet established minimum requirements for standardization; even the mouse potency assay may not be suitable. There are techniques, however, which will measure amounts of component antigens and toxicity. Conflicting results on assays of potency and immunogenicity will have to be resolved. Besides the obvious need for large clinical trials of defined vaccines, a whole range of research needs were suggested, from genetic studies of the organism to specific details of the host response. It is generally agreed that a less reactogenic and more effective pertussis vaccine is needed and feasible.