RESUMO
Intestinal immunity was studied in a polio-free community immunised with a combined enhanced inactivated/oral polio vaccine (EIPV/OPV) vaccination programme. Poliovirus excretion was evaluated in three groups of infants primed with a partial (2 EIPV+2 OPV) or complete (3 EIPV+3 OPV) dose schedule. Poliovirus replicated in the gut of 59.8-55.8% of infants in the three groups 7 days after administration of an additional OPV dose. Significant decreases in the percent of type-specific-virus excreters appeared after 14 and 21 days for serotypes 1 and 2, and after 21 and 28 days for serotype 3. The percent of excreters was inversely correlated with pre-challenge neutralising antibody (NA) titers (p<0.05). Intrafamilial virus transmission to mothers and siblings was minimal. The principal factor for interruption of disease and virus transmission in the community was a strong and persistent humoral immunity with immunological memory. A satisfactory level of family hygiene contributed towards breaking the chain of transmission of poliovirus to contacts.