A seroepidemiological study on the level of immunological coverage in a nomadic population in Rome]

Immunization status to the three types of poliovirus, to tetanus, diphtheria and measles was evaluated in a Gypsy population living at a Roman camp. Information about demographic data and history of immunization was collected from 149 subjects and a blood sample was obtained from 86 individuals to determine antibody titres to the above mentioned infectious agents. Among the responders, only 20.8% had received at least one dose of oral polio vaccine (OPV), tetanus and diphtheria vaccine, while none was vaccinated against measles. In spite of a low immunization coverage, serological data showed high prevalence of antibodies to the three types of poliovirus (81.4% to polio type 1:94.2% to polio type 2:62.8% to polio type 3) and to measles (76.7%), while antibodies to tetanus and to diphtheria were detected respectively only in 3.5% and 0% of the individuals tested. High levels of antibodies to polio were found also among unvaccinated subjects. For these, a statistically significant positive correlation between age and number of "contact doses" from vaccinated family members was observed (r = 0.70; CI 95%: 0.27-0.90). In conclusion, this study uncovers very low levels of immunization to poliovirus, tetanus, diphtheria and measles in the study Gypsy population, and shows the effects of the secondary spread of the OPV, which probably contributed to reduce the risk of contracting the disease in unvaccinated individuals.