The WHO-EPI initiative for the global eradication of poliomyelitis.

Since the development of attenuated oral polio vaccine, Dr Albert Sabin consistently maintained that the global eradication of wild poliovirus was possible, but that to achieve polio eradication in developing countries would require the mass administration of the oral vaccine. Experience in Cuba and Czechoslovakia proved the effectiveness of this technique, but it was only with its deployment in Brazil in 1980 that its role in eradicating the virus from a broad geographical area started to be realized. With the declaration in 1985 of a target of regional polio eradication, extension of this policy, allied with the development of effective surveillance of acute flaccid paralysis in children, with laboratory confirmation of diagnosis rapidly led to apparent interruption of wild poliovirus transmission throughout the Americas. The World Health Assembly in 1988 committed WHO to the global eradication of poliomyelitis. Based on experience in the Americas and building on the solid foundation established by the Expanded Programme on Immunization, WHO has defined the strategies through which the global target could be achieved. Progress is encouraging and where the advocated strategies have been fully implemented, the incidence of poliomyelitis has declined dramatically. Significant geographical areas in Western Europe, the Maghreb, the Arabian peninsula, the Pacific basin and Southern Africa, each incorporating several countries, are now thought to be free of the disease caused by wild poliovirus. The target of a world free of polio by the year 2000 can be achieved.

Studies of missed opportunities for immunization in developing and industrialized countries.

Missed opportunities for immunization are an obstacle to raising immunization coverage among children and women of childbearing age. To determine their global magnitude and reasons, studies reported up to July 1991 were reviewed. A standard measure for the prevalence of missed opportunities was calculated for each study. Seventy-nine studies were identified from 45 countries; 18 were population-based, 52 were health-service-based, and 9 were intervention trials. A median of 32% (range, 0-99%) of the children and women of childbearing age who were surveyed had missed opportunities during visits to the health services for immunization or other reasons. Missed opportunities were mainly due to failure to administer simultaneously all vaccines for which a child was eligible; false contraindications; health workers' practices, including not opening a multidose vaccine vial for a small number of persons to avoid vaccine wastage; and logistical problems. To eliminate missed opportunities for immunization, programmes should emphasize routine supervision and periodic in-service training of health workers which would ensure simultaneous immunizations, reinforce information about true contraindications, and improve health workers' practices.

PIP: The authors review studies reported up to July, 1991, on the global magnitude of and reasons for missed opportunities to immunize children and women of childbearing age. A standard measure was calculated for the prevalence of missed opportunities for each of the 79 studies identified from 45 countries; 18 were population-based, 52 were health-service-based, and 9 were intervention trials. A median of 32% over a range of 0-99% children and women of childbearing age surveyed had missed opportunities during visits to health services for immunization or other reasons. These outcomes were due mainly to the future to administer simultaneously all vaccines for which a child was eligible; false contraindications; health workers' practices; and logistical problems. To eliminate these missed opportunities, programs should emphasize routine supervision and the periodic in-service training of health workers. This approach would ensure simultaneous immunizations, reinforce information about true contraindications, and improve health workers' practices.

EPI for the 1990s. The Expanded Programme on Immunization Team.

This paper highlights the achievements, lessons learned, goals, policies, strategies and approaches for the Expanded Programme on Immunization for the 1990s. The Programme's Global Advisory Group endorsed the paper in October 1991, together with actions proposed for the 1990s. Figures showing immunization coverage and estimates of prevented and current mortality and morbidity are included.

The expanded programme on immunization: a decade of progress in India.

The Expanded Programme on Immunization (EPI) was initiated in India in 1978 with the objective to reduce morbidity and mortality from diphtheria, pertussis, tetanus, poliomyelitis and childhood tuberculosis by providing immunization services to all eligible children and pregnant women by 1990. Measles vaccine was included when the EPI was accelerated by launching the Universal Immunization Programme (UIP) in 1985-6. Approximately half of all infants now receive complete primary immunization with diphtheria, polio and tetanus (DPT), oral polio vaccine (OPV) and BCG vaccine. Forty-six per cent of pregnant women currently receive a second or booster dose of tetanus toxoid (TT). Surveillance reports from selected areas have documented impact through reduction of disease incidence. Although vaccination coverage levels are increasing, continued acceleration is needed to achieve the universal levels targeted for 1990.

Poliomyelitis surveillance and vaccine efficacy in Bombay, 1982-87.

Reported are updated data on poliomyelitis surveillance in Bombay for the period 1982-87 and estimates of the efficacy of oral poliovaccine (OPV) calculated by the case exposure method, using two approaches. The first, a screening technique that used only data on the reported number of doses of vaccine administered and the immunization status of all poliomyelitis cases, appeared to underestimate the true vaccine efficacy. In the more rigorous second technique, which used data for children of the same age group, geographical areas, and study year, obtained from immunization coverage surveys, and information on the immunization status of poliomyelitis cases, the results indicate that the OPV vaccine efficacy for fully immunized children aged 12-23 months exceeded 90%. These findings show that the estimated efficacy of OPV is high in Bombay and that, in general, vaccine efficacy should be re-estimated using more rigorous techniques if preliminary screening estimates indicate a lower than expected efficacy. In Bombay, poliomyelitis therefore results primarily from a failure to fully vaccinate all eligible children rather than as a result of vaccine failure. Furthermore, the age distribution of cases suggests that the strategy of focusing immunization activities on children aged under 1 year is epidemiologically correct.

Poliomyelitis surveillance and vaccine efficacy in Bombay, 1982-87

Reported are updated data on poliomyelitis surveillance in Bombay for the period 1982-87 and estimates of the efficacy of oral poliovaccine (OPV) calculated by the case exposure method, using two approaches. The first, a screening technique that used only data on the reported number of doses of vaccine administered and the immunization status of all poliomyelitis cases, appeared to underestimate the true vaccine efficacy. In the more rigorous second technique, which used data for children of the same age group, geographical areas, and study year, obtained from immunization coverage surveys, and information on the immunization status of poliomyelitis cases, the results indicate that the OPV vaccine efficacy for fully immunized children aged 12-23 months exceeded 90 percent

These findings show that the estimated efficacy of OPV is high in Bombay and that, in general, vaccine efficacy should be re-estimated using more rigorous techniques if preliminary secreening estimates indicate a lower than expected efficacy. In Bombay, poliomyelitis therefore results primarily from a failure to fully vaccinate all eligible children rather than as a result of vaccine failure. Furthermore, the age distribution of cases suggests that the strategy of focusing immunization activities on children aged under 1 year is epidemiologically correct(AU)

Immunization in urban Southeast Asia.

By the year 2000 half the population in the world is expected to reside in large urban areas. "Improving immunization services to the disadvantaged in urban areas" is considered one of the priorities for the Expanded Programme on Immunization (EPI). A review of the current situation with regard to immunization coverage and disease surveillance in urban Southeast Asia shows that acceleration of immunization activities in urban areas is needed to achieve and sustain the goal of Universal Child Immunization by the year 1990.

Silica gel as transport medium for Corynebacterium diphtheriae under tropical conditions (Indonesia )

Silica gel was confirmed as a useful transport medium for Corynebacterium diphtheriae in the investigation of diphtheria cases in which there is no ready access to laboratory facilities.

Diphtheria: a possible foodborne outbreak in Hodeida, Yemen Arab Republic.

Between 29 August 1981 and 16 January 1982, an epidemic of diphtheria produced 149 cases in Hodeida, Yemen Arab Republic. The overall attack rate was 11.8 per 10 000; the most frequent victims were males under 5 years of age, with an attack rate of 55.7 per 10 000. Severity of the illness varied inversely with age and the number of previous doses of DPT. A case-control study showed that vaccination with DPT was protective (P = 0.03) with an efficacy of 87.3% (95% confidence interval, 32.2-99.5%) among those who had received 3 or more doses. Risk factors for the development of disease were previous contact with a case (P = 0.002), previous contact with a person having skin disease (P = 0.04), obtaining drinking-water from a wheeled carrier (P = 0.008), and consumption of factory-made yoghurt (P = 0.003). The secondary attack rate among household contacts under 15 years of age was at least 1.3%.

Poliomyelitis in the USA: virtual elimination of disease caused by wild virus.

The average number of paralytic poliomyelitis cases per year in the United States has fallen from 16 000 just before vaccine was introduced in the 1950s to only 12 in 1978-83. 18 of the 69 cases (26%) reported in this 6-year period were not vaccine associated according to the epidemiological classification of paralytic poliomyelitis cases, established in 1975. The van Wezel antigenic differentiation test and oligonucleotide fingerprinting provide a laboratory basis for definitive characterisation of wild and vaccine-like poliovirus strains. Of the 69 cases, isolates from 42 have been analysed; 31 were vaccine-like poliovirus and 11 wild poliovirus. 7 of the wild poliovirus isolates are from cases in a 1979 outbreak caused by poliovirus imported from the Netherlands through Canada; 1 is from a single importation; and 3 are from isolated cases with no identified source. No indigenous wild strain has been isolated from any reported poliomyelitis case since 1981, when a wild strain was isolated from an immunodeficient individual.