[Anti-HBs persistence after revaccination with three doses of hepatitis B vaccine among low-responder infants following primary vaccination: 4-year of follow-up].

Assess the 4-year antibody against hepatitis B surface antigen (anti-HBs) persistence after revaccination with 3-dose of hepatitis B vaccine (HepB) among low-responder infants following primary vaccination. According to stratified cluster sampling, a total of 4 147 infants were enrolled and primarily vaccinated with 5 μg HepB derived in Saccharomyces Cerevisiae (HepB-SC) at 0-1-6 months schedule from 75 towns of Jinan, Weifang, Yantai, Weihai prefectures, Shandong Province, China in Aug and Sep 2009. Blood samples were collected one to six months after the third dose of primary immunization and tested for anti-HBs using chemiluminescence microparticle immunoassay (CMIA). 717 infants who appeared low response (10 mU/ml ≤ anti-HBs<100 mU/ml) were revaccinated with 3-dose of HepB. Blood samples were collected from a total of 315 infants one month (T(0)), four years (T(1)) after revaccination and anti-HBs, antibody against hepatitis B core antigen (anti-HBc) and hepatitis B surface antigen (HBsAg) were detected by CMIA. Information about their birth, primary vaccination were collected. The risk factors associated with positive rate of anti-HBs and GMC of anti-HBs were identified by multiple non-conditional logistic regression analysis and multifactor linear regression model analysis, respectively. Among 315 children, 165 (52.38%) were male and 150 (47.62%) were female. The positive rate was 83.81% (264/315) at T(0) and it decreased to 16.51% (149/529) at T(1). The corresponding GMC decreased from 473.15 mU/ml to 17.37 mU/ml. The average annual decreasing rate of positive rate and GMC was 33.38% and 56.23% from T(0) to T(1). Multivariable analysis showed the positive rate and GMC among those whose anti-HBs titer higher at T(0) were significantly higher at T(1). The positive rate at T(1) among those whose anti-HBs titer 400-<600, 600-<800, 800-<1 000, ≥1 000 mU/ml at T(0) were significantly higher than those whose anti-HBs titer less than 200 mU/ml. The (95) of the positive rate was 4.29 (1.03-17.84), 4.53 (1.25-16.47), 4.19 (1.10-15.97) and 9.13 (2.91-28.63), respectively. The GMC at T(1) among those whose anti-HBs titer 400-<600, 600-<800, 800-<1 000 mU/ml and those whose anti-HBs titer ≥1 000 mU/ml at T(0) were higher than those whose anti-HBs titer200 mU/ml. The value (95) of GMC was 0.84 (0.06-1.62), 1.13 (0.46-1.79), 1.33 (0.65-2.01) and 1.88 (1.33-2.44), respectively. GMC among full-term infants were significantly higher than premature infants at T(1). The value (95) of GMC was 0.86 (0.04-1.68). Anti-HBs GMC decreased rapidly 4 years after revaccination among low-responder infants, but still kept good protection. The anti-HBs persistence after revaccination was associated with anti-HBs level of titer one month after revaccination.