The work of the WHO Consultative Group on Poliomyelitis Vaccines.

PIP: Through a review of the work on the control of poliomyelitis carried out under the auspices of the World Health Organization (WHO) during the past 20 years, the importance of international collaboration is shown. Because of efforts in planning and coordinating, the production and control of the Sabin strains of the live oral vaccine provide safe, reliable, and potent vaccines. The cooperative efforts have included working not only with national control laboratories but with poliomyelitis vaccine producers in many countries. In the early 1970s, a Consultative Group of WHO became active. Their initial efforts included an extensive epidemiological study in 13 interested countries. Later, the group saw to studying the reliability of the marker tests used in the intratypic differentiation of poliovirus stains of different origins. Additionally, they saw to standardizing tests for the neurovirulence of vaccine lots, including analyzing and recording results, and to ensuring that adequate supplies of vaccine will be available for the next 200 years. After 15 years of continual surveillance of vaccine-associated cases by WHO epidemiologists and clinicians, the findings show the following: Type 1 live poliovirus vaccine is almost never implicated in postvaccination paralysis; type 2 strain occasionally causes of paralysis in contacts of the vaccine, and type 3 strain causes most of the few cases of postvaccine paralysis. The occurrences of the cases from type 2 and 3 strains remains an enigma. Current research of the group suggests an even more effective vaccine may become available in the future.^ieng

A seven-year study of WHO virus laboratory reports on respiratory viruses.

In 1963 the World Health Organization established a system for the collection and distribution of information on viruses. By 1973 laboratories in 45 countries were participating in this scheme. The present study is an analysis of the reports on adenovirus, influenza viruses A, B, and C, parainfluenza virus, respiratory syncytial (RS) virus, rhinovirus, and Mycoplasma pneumoniae during 1967-73. In the northern hemisphere, from which over 95% of the reports were received, a clear pattern of the seasonal incidence of different respiratory tract infections emerged. Over 70% of the total number of reported adenovirus infections, over 80% of the parainfluenza virus infections, and over 90% of the RS virus infections were in children. M. pneumoniae infections were most frequently reported in adults. Influenza A virus infection was predominant in the adult population, with a high proportion in those aged 60 years and over. Influenza B infections were reported equally in adults and children, but over one third were in children of school age. The proportion of lower respiratory infections to total respiratory infections varied from one virus to another, and ranged from less than half for adenovirus to over four fifths for mycoplasma infections. Nonlocalizing fever was usually the second principal clinical condition reported in association with respiratory viruses.

Some observations on the communicable diseases as public health problems.

Notwithstanding the deficiencies in reporting, an attempt is made in the present study to provide some useful information on the importance of the communicable diseases in the world over the decade 1957-58 to 1967-68. In this period health authorities in the developing countries almost invariably reported communicable diseases as their main public health problems, whereas, in the developed countries, the only communicable diseases still considered as public health problems were tuberculosis, venereal diseases, and hepatitis. In the developing countries nearly half of the principal causes of death were communicable diseases, and in both the developing and developed countries respiratory infections ranked high on the list. Deaths from tuberculosis have come down markedly in the developed countries and to a lesser degree in the developing countries. Infectious diseases of childhood are no longer a problem in the developed countries but are still important in the developing countries. The communicable diseases of importance to the developing countries may be divided into two groups-those requiring long-term development for their solution (e.g., dysentery, typhoid fever, parasitic diseases, and respiratory infections) and those that would respond rapidly to control by such methods as immunization.

Use of excess mortality from respiratory diseases in the study of influenza.

Since 1970, WHO has conducted a collaborative study on the use of "excess mortality" from respiratory diseases (that is, the number of deaths actually recorded in excess of the number expected on the basis of past seasonal experience) in order to assess in 13 different countries the severity of influenza epidemics. The use of computer-produced seasonal expected and actual curves permits quick visual assessment of influenza activity in any one country, as well as comparisons between different countries. The study demonstrates that an excess in the observed over the expected number of total deaths does not necessarily indicate an excess in deaths from influenza, and it is therefore limited, at least for the present time, to deaths from respiratory disease. It provides a week-to-week record of deaths from acute respiratory disease in countries where weekly returns are available and a retrospective analysis of the disease pattern in the collaborating countries. This study will be continued for a number of years and, apart from its value to the individual countries, should provide useful comparisons between countries with different climates.

Routine administration of oral polio vaccine in a subtropical area. Factors possibly influencing sero-conversion rates.

Poliomyelitis is an important problem of public health in warm-climate countries. Studies of serological responses to vaccination in these countries have given conflicting results but in many investigations the rates have been considerably less than in countries with temperate climates. In this study three possible factors influencing sero-conversion were investigated - the season of the year when vaccine was given, the social status of the mother (as indicated by the number of years of schooling) and the presence of non-poliomyelitis viruses (NPV) in the gut when vaccine was given.Over 200 children about 2 months of age were included in the study. Each was given three doses of trivalent vaccine at 6-week intervals.The sero-conversion rates of the groups fed in winter were excellent but were slightly less good in summer. The differences were greatest in children in the lower socio-economic groups and in children excreting other enteroviruses.The conclusions are that, provided a potent vaccine is used, the factors which diminish the effectiveness of immunization in warm-climate countries can be overcome: (1) by giving three doses of trivalent vaccine; (2) by beginning vaccination at the earliest possible age (when enteroviruses are fewest); (3) by concentrating special attention on the lower socio-economic groups and if necessary by giving a reinforcing dose several months after the third dose has been given - preferably in the colder months.