<0.1 IU/ml Insufficient immunity, booster vaccination recommended
0.1-0.5 IU/ml Immunity given, booster vaccination will provide long-term immunity
>0.5-1.1 IU/ml Sufficient immunity, booster vaccination in 2 to 5 years
>1.1-5.0 IU/ml Sufficient immunity, booster vaccination in 5 to 10 years
>5.0 IU/ml Sufficient immunity, booster vaccination in approx. 10 years