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 18-79 years). Furthermore, sera from persons aged less than 18 years were included (n = 881). 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 1, 0.180 IU/ml for Polio 2 and 0.080 IU/ml for Polio 3. Neutralizing antibodies against poliovirus type 1, 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.