Immunity status against poliomyelitis in Germany: Determination of cut-off values in International Units

Background To prevent importations of wild polioviruses into a polio free region a high level of population immunity must be kept. Standard methodology for determination of polio antibodies is a feature aimed at obtaining consistent results. An International Standard Serum for polio antibodies exists, but no protective level in International Units is defined. Methods A representative study was carried out in order to determine the serological status against poliomyelitis in Germany (n= 2564, age 8 - 79 years). Furthermore, sera from persons aged less than 8 years were included ( n= 88). Microneutralization test has been used for determination of antibody levels. Results have been expressed in International Units. Results The results of this study indicate that the cut-off level for polio antibodies is 0.075 IU/ml for Polio, 0.80 IU/ml for Polio 2 and 0.080 IU/ml for Polio 3. Neutralizing antibodies against poliovirus type, 2 and 3 were detected in 96.2%, 96.8% and 89.6% of samples, respectively. Conclusions Overall, this seroprevalence indicates a very high level of immunity of the general population. It must be kept after the switch of immunization strategy from attenuated to inactivated vaccine in Germany.