Secretory and serum immunoglobulin class-specific antibodies to poliovirus after vaccination

Immune responses in serum and saliva were studied in Pakistani children by enzyme-linked immunosorbent assay after natural exposure to poliovirus and vaccination with live or inactivated poliovirus vaccines. Swedish children unexposed to wild poliovirus who had almost 1000/0 vaccination coverage with inactivated vaccine at 8, 9, and 18 months and at 5 years of age were analyzed for comparison. Natural exposure induced secretory IgA (SIgA) antibodies to poliovirus in the saliva of Pakistani infants at one month of age that reached adult levels at six months. No difference in levels of salivary antibody at eight months was observed between groups vaccinated with either live or inactivated vac-cines. Vaccination with live or inactivated vaccine starting at 2 or 3 months of age resulted in high titers of IgG antibody to poliovirus in serum, the highest of which occurred after four doses of live vaccine. In Sweden, an increase of antibody in serum was observed after the third vaccination. IgA antibodies continued to increase subsequently, whereas IgG antibodies reached a plateau. The SIgA response in saliva initially appeared on the third vaccination, with a significant increase after the fourth. Repeated vaccination with inactivated poliovirus vaccine induces specific SIgA antibodies. Adults all had SIgA anti