hepatitis b virus ( hbv ) belongs to family hepadnaviridae and is a dna virus . although hbv vaccine is currently used , hbv infection remains one of the 10 most common causes of the death worldwide . about 400 million of the world population is infected with hbv , and around 250,000 people die each year from hbv related liver disease such as cirrhosis and hepatocellular carcinoma ( 1 ) . they are also at risk of incidents like needle stick , sharp injuries , and the like that could make the transmission of hbv infection easy through health care workers ( 3 ) . the risk of acquiring hepatitis b infection among the health care workers is about 10 times higher than other groups ( 4 ) . the hbs antibody has an important role in the protection against hbv infection ( 5 ) . the expression of antiviral , th1 cytokines such as gamma interferon ( ifn- ) and tumor necrosis factor- ( tnf- ) can control hepatitis b infection ( 6 ) . hepatitis b vaccine can motivate the immune system to produce both hbsab and specific hbs gamma interferon ( 7 ) . immunization with hepatitis b vaccine at first day , 30th day , and 180th day can create 90% and 95% protection in adults and children , respectively ( 8) . antibody protection for general population is found at the titer of > 10 miu / ml ( 9 , 10 ) . persons with anti - hbs titer < 10 miu / ml are defined as non - responder , and persons with anti - hbs titer > 10 and < 99 miu / ml are defined as hyporesponders . they usually show shorter period of detectable antibody called  waning antibody  or  waning immunity  ( 11 , 12 ) . this study aimed to evaluate the titer of hbsab among the vaccinated health care workers of the golestan hospital in ahvaz , iran . this cross - sectional study was carried out on 39 health care workers , including 13 general surgeons , 10 anesthesiologists , 5 neurosurgeons , 3 general physicians , 1 orthopedist , 2 urologists , and 5 nurses from golestan hospital in ahvaz , during 2013 . among them , 24 ( 61.5% ) were males and 15 ( 38.4% ) were females . the health care worker s age ranged from 24 to 58 years with the mean age of 34.3  7.4 y. then , they grouped based on their hbsab titer : < 10 , 11 - 100 , and > 100 miu / ml . another classification was done based on cases with antibody titer lower than 10 miu / ml and higher than 10 miu / ml for doing more statistical analysis . based on our findings , hbsab titer was lower than 10 miu / ml in 12.8% ( 5 ) of participants . it was between 11 and 100 miu / ml in 30.8 % ( 12 ) of them . and finally , the titer was higher than 100 in 56.4% ( 22 ) of cases . vaccination history of health care workers and their antibody titer were showed in table 1 . all the health care workers had history of the needle stick injuries for several times . initially , a 5-ml blood sample was taken from each healthcare worker in a glass tube containing edta . after centrifugation , the plasma was collected and tested for the titer of anti - hbsab and detection of hbc - igg , using elisa kit ( diapro , italy ) according to the manufacturer s instruction . peripheral blood mononuclear cells were isolated from fresh blood supplemented with edta by ficoll - hypaque ( baharafshan , iran ) density gradient centrifugation . briefly , 5 ml blood sample was added to a glass tube containing 2 ml ficoll followed by centrifugation for 20 minutes at 2500 rpm . one hundred and seven mononuclear cells of each health care worker was resuspended in rpmi 1,640 medium , supplemented with 2 mmol / l l - glutamine , 1 mmol / l sodium pyruvate , 100 u / ml penicillin , 100 u / ml streptomycin , and 2.5 g amphotericin b. next , 2.5 g purified recombinant hbs vaccine was added to each well containing 107 mononuclear cells . supernatant was aspirated and the concentration of interferon  was measured by human interferon  elisa test kit ( ebioscience , vienna , austria ) according to manufacturer s instructions . chi - square test was done and p value of < 0.05 was considered statistically significant . initially , a 5-ml blood sample was taken from each healthcare worker in a glass tube containing edta . after centrifugation , the plasma was collected and tested for the titer of anti - hbsab and detection of hbc - igg , using elisa kit ( diapro , italy ) according to the manufacturer s instruction . peripheral blood mononuclear cells were isolated from fresh blood supplemented with edta by ficoll - hypaque ( baharafshan , iran ) density gradient centrifugation . briefly , 5 ml blood sample was added to a glass tube containing 2 ml ficoll followed by centrifugation for 20 minutes at 2500 rpm . one hundred and seven mononuclear cells of each health care worker was resuspended in rpmi 1,640 medium , supplemented with 2 mmol / l l - glutamine , 1 mmol / l sodium pyruvate , 100 u / ml penicillin , 100 u / ml streptomycin , and 2.5 g amphotericin b. next , 2.5 g purified recombinant hbs vaccine was added to each well containing 107 mononuclear cells . supernatant was aspirated and the concentration of interferon  was measured by human interferon  elisa test kit ( ebioscience , vienna , austria ) according to manufacturer s instructions . chi - square test was done and p value of < 0.05 was considered statistically significant . out of 39 health care workers , 24 ( 61.5% ) were male and 15 ( 38.4% ) were female . the health care worker s age was between 24 and 58 years with the mean age of 34.3  7.4 years . none of the health care workers were smoker ; they were not overweight and did not have chronic liver disease , lung , or kidney disease . about 28 ( 80% ) health care workers had received three doses of vaccine or more ( table 2 ) . on the basis of hbsab titer group 2 had hbsab titer between 10 and 100 iu and group 3 had hbsab titer above 100 iu . about 34 ( 87.2% ) health care workers showed hbsab response to the vaccine as higher than 10 miu / ml . twenty - two ( 56.4% ) health care workers who had received last dose of vaccine 6.6  4.3 years ago had titer of hbsab higher than 100iu / ml . seventeen ( 43.6% ) subjects who had received last dose of vaccine 10  4.06 years ago , showed hbs titers lower than 100 iu and 3 ( 7.7% ) health care workers were positive for hbc - igg and hbsab but negative for interferon . tables 3 and 4 show the measurement and distribution of hbsab and interferon  among the health care workers in different age groups . table 3 indicates that first group had better response to vaccine ( or : 3.11 ) compared to other age groups . the mean of 18.9  36.5 pg/l of the specific interferon  response was observed in the age group ( 30 - 39 ) that was higher than other age groups . twenty - seven ( 69.2% ) health care workers had positive specific interferon  response against hbv vaccine , while 12 ( 30.8% ) cases were negative for specific  interferon ( table 4 ) . the risk of acquiring hepatitis b virus ( hbv ) infection is high among health care workers ( hcws ) because of their much exposure to blood or its products . one study reported that 23% of the health care workers of national iranian oil company had exposure to hbv infection ( 13 ) . this report suggests that injection of hepatitis b immunoglobulin should be mandatory in those health care workers who had negative hbsab . based on reports , about 13% to 60% of individuals who have received first hbv vaccine may lose antibody against hepatitis b virus later ( in years ) ( 10 ) . it seems that a booster hbv vaccine could be useful for those health care workers that recognized as hyporesponders ( immunity lower than 100 iu / ml ) .   in iran , some studies showed the persistence of hepatitis b antibody ( anti - hbs ) in 47%-80% of people who received the last dose of vaccine 10 - 16 years ago ( 14 - 16 ) . in this study , the age group ( 20 - 29 years ) shows better antibody response ( or : 3.11 ) compared to other groups , which is similar to previous reports ( 12 , 17 ) . the age group ( 30 to 39 ) shows better gamma interferon response to hbv vaccine , although 12 ( 30.7% ) health care workers were negative for gamma interferon , which is consistent with the findings of lu et al . there was no significant difference in the rate of high anti - hbs titer ( > 100 iu / ml ) between females and males ( p > 0.05 ) ; however , some studies reported that females show better response to hbv vaccine than males ( 12 ) . we found that in 87.1% of individuals who received hbv vaccine , hbsab titer is higher than 10 miu / ml , which is similar to report of bahmani et al . twenty - seven ( 69.2% ) health care workers had positive specific interferon  response against hbv vaccine . interferon  plays an important role in the prevention of hbv infection in the presence of low titer of hbsab ( 18 ) . previous reports have shown that increase in interferon  expression in coordination with cd8 and cd4 t cell will help to complete virus clearance ( 20 ) . other studies suggest that increase in interferon  concentration will decrease serum hepatitis b viral load . it means that hepatitis b viral load and interferon  level have negative correlation ( 21 ) . in this study , 12 ( 30.7% ) health care workers were negative for interferon . only 2 ( 5.1% ) of them received last dose of hbv vaccine about two years ago , however they had high titer of hbsab . it is estimated that about 5% to 7% of the population are nonresponsive to vaccine . it could be due to a sort of defectiveness in specific t or b cell generation , expression of some kind of leukocyte antigens ( hla ) , degradation of b cells by cytotoxic t cell , tolerance or even imbalance in t - helper cells ( 12 , 22 ) . some of hla antigens like dr7 dr3 and dq2 have negative effects on vaccination outcome and cytokine secretion like interferon  ( 23 ) . in our study , hla antigens of health care workers were not investigated , but it could be a reason for decrease in interferon  concentration in some cases . in our study , 3 ( 7.7% ) cases were positive for anti hbc , which indicates the presence of the past hbv infection . ( 17 ) reported that 6.4% of the health care workers had positive hbc - igg . all three cases were surgeons , probably because of their occupation , which is a risk factor for hbv infection
background : health care workers are at high risk of acquiring hepatitis b virus ( hbv ) infection through occupational exposure to blood or body fluids . thus , the assessment of anti - hbs status after immunization is very important.objectives:this study aimed to evaluate the measurement of hbsab titer and specific gamma interferon response among the vaccinated health care workers in golestan hospital , ahvaz , iran.patients and methods : the blood samples of 39 health care workers , including 13 general surgeons , 10 anesthesiologists , 5 neurosurgeons , 3 general physicians , 1 orthopedist , 2 urologist and 5 nurses were collected during june 2013 . 
 all the participants had received hbv vaccine . 
 they had received last vaccine dose from 2 months to 14 years ago . 
 their sera were tested for anti - hepatitis b antibody and hbc - igg by the elisa . 
 also , the evaluation of specific interferon  response against hbsag was carried out using elisa test . 
 the age of health care workers were between 24 and 58 years with the mean age of 34.3  7.4 y.results:out of 39 sera , 22 ( 56.41% ) had hbsab titer above 100 iu / ml , 17 ( 43.6% ) had titer below 100 iu / ml , 27 ( 69.2% ) had positive specific hbsag interferon  , 8 ( 20.5% ) cases had positive antibody response above 100iu , but negative for specific interferon  and 3 ( 7.6% ) cases were positive for hbc-igg.conclusions:overall , 87.2% of the health care workers had immunity against hbv infection , which showed remarkable immunity response following hbv vaccination 
 . booster dose of hbv vaccine is recommended for those whose immunity are below 100 iu / ml .