INFLUENCE OF HOST RELATED FACTORS ON THE ANTIBODY-RESPONSE TO TRIVALENT ORAL POLIO VACCINE IN TUNISIAN INFANTS

The low efficiency of trivalent oral polio vaccine (TOPV) in inducing protective antibody titres to polio3 is a problem of great importance in many regions of the world. A prospective study was conducted in 121 Tunisian infants aged 3 months during routine immunization with TOPV under carefully controlled conditions. Seroconversion rates to polio1, polio2 and polio3, one month after the third dose, were 94.7, 100 and 89.5%, respectively. The kinetics of the antibody response showed del ayed and more difficult responses to polio3 compared to polio2 and pol io1. The following host related factors, previously suggested to inter fere with the immune response, were assessed: maternal antibodies; bre ast-feeding; concurrent enteric infections, and other illnesses. The m ain factor associated with the lack of seroconversion was concurrent i nfection with non-polio enteroviruses (NPE) which was found in 50%; of non-responders to polio1 and/or to polio3 during the vaccination prot ocol whereas no NPE was isolated in vaccine responders. The other stud ied factors seemed not to interfere in the infants according to the lo cally adopted vaccination schedule and to the specific socio-economic conditions. (C) 1997 Elsevier Science Ltd.