Unimmunized Gypsy populations and implications for the eradication of poliomyelitis in Europe.

The certification of poliomyelitis eradication in Europe will eventually require that countries demonstrate there is a minimal risk of wild poliovirus reintroduction and sustained transmission through unimmunized subpopulations such as ethnic minorities. A serologic survey among a Gypsy community in Italy found that despite only 26% documented immunization coverage, serum neutralizing antibodies to poliovirus types 1, 2, and 3 were detected in 81%, 94%, and 63% of the 86 persons studied. While the high level of immunity found in this community may have been due to secondary spread of vaccine virus, the possibility of unrecognized circulation of wild polioviruses cannot be excluded. Targeted immunization of such groups may be the most efficient means of eliminating the risk of importation-associated outbreaks.