Review of poliomyelitis in Bombay (1982-1989): observations on the improved immunisation coverage

In Bombay, the immunization coverage with 3 doses of oral polio vaccine in children below 2 years of age has reached 80%. As a result, the high incidence of over 11/100,000 population prevailing in the 6 year period (1982-1987) has declined to around 6 in 1988 and 1989. The decline was observed both in the slum and in the "non-slum" population. The incidence in the slum population has reduced from over 22/100,000 population to around 11. In the morbidity, a subtle "age shift" to older children was noticed in 1988-1989. Average age-specific incidence (for age group below 1 year) was found to be 1.04/1000 children in 1988-89 as against 2.47 in the preceding 6 years. The proportion of "Non-Immunized" cases gradually declined from 65.8% in 1982 to 49.7% in 1989 and conversely, the proportion of fully immunized cases increased from 14.5% in 1982 to 22.7% in 1989. The attack rates per 1000 children below 1 year of age in the inadequately/"Non-Immunized" and the fully immunized children were found to be 2.822 and 0.224 respectively. The sharp peak in the morbidity observed in the 3rd quarter of an year (July to September) has been replaced by almost even distribution of cases in all the quarters of an year. All the three polioviruses were encountered through out the year. Although, poliovirus type 1 was the most predominant of viruses, its proportion was on decline. The portion of isolation of "Non-Polio" viruses has increased from 6.8% in 1982 to 16.2% in 1989.(ABSTRACT TRUNCATED AT 250 WORDS)