One of our main findings was the detection of higher frequencies of CD24+CD27+ and CD24highCD38high Breg accompanied by lower levels of IL-10 expression in 2nd HBvac NR compared to R. So far, very few studies investigated the association of Breg frequencies and IL-10 expression levels with non-responsiveness to hepatitis B vaccination (12, 38, 39). This evidence concerns the gene IL10 and hepatitis B virus infection.