Further clarity on vaccine-associated paralytic polio in India [letter]

Our findings demonstrate that the risk of VAPP is lower in India compared to previous analyses in Latin America or in industrialized countries. Since we reported our findings surveillance data from India for 2000 and 2001 have become available. These data show a decreasing trend in the total number of VAPP cases from 181 in 1999 to 129 in 2000 and 109 in 2001 suggesting that the 1999 data (and associated risks) were not stable. Massive exposure to more than 750 million doses of OPV in India in 1999 alone probably resulted in a ‘‘catch-up phenomenon’’ exposing many children to the first ‘‘immunizing’’ dose of OPV with the associated increased risk of VAPP. Only data from subsequent years will allow calculation of a more precise VAPP estimate under conditions approximating a steady state in India. (excerpt)