An outbreak of poliomyelitis in Andhra Pradesh (South India)

An outbreak of poliomyelitis that occurred in the year 1992 in Telangana region of Andhra Pradesh, South India was investigated to understand the reasons for persistence of poliomyelitis in the general population and for the outbreak in Andhra Pradesh in particular. The study comprised of a detailed investigation of epidemiological and clinical features, serology and vaccination status and a case control study to calculate vaccine efficacy by matched pair analysis. The outbreak occurred after a relative quiescence of 3 years. The age group of the patients ranged from 2 months to 5 years, 26.5% being infants and 70.2% being children between 1 and 5 years. The outbreak was mainly caused by Type 1 poliovirus. Vaccine efficacy was found to be 70%. Antibody response was not high in cases. Seventy six per cent of the children with poliomyelitis were unvaccinated. Ignorance of the mothers and family interference were the main causes for not vaccinating the children. The study indicates the need to increase the vaccination coverage and inclusion of children upto 5 years in the programme. Absence of vaccination is the major risk factor for the outbreak. The persistence of poliomyelitis in older children, low antibody response and suboptimal vaccine efficacy point out the problem of achieving control with OPV in tropical countries and suggest the need for alternate strategies. Better health education strategies need to be developed.