2215
After hepatitis B vaccine immunization , serum antibody response was of primary type in 33 cases with anti - HBs less than 2 . 1 S / N ( S / N Ratio Unit ) at T0 , the anti - HBs positive rate was 39 . 4 % , 84 . 8 % , 96 . 7 % and 96 . 7 % in T1 , T2 , T0 and T12 respectively .
 anti - HBs, anti - HBs
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 anti - HBs, anti - HBs