RESUMO
To explore the possible risk factors for failure to seroconvert after vaccination of healthy subjects against hepatitis B [HB]. This study comprised 381 healthy employees at the Armed Forces Hospitals [AFH] in the southern region, Khamis Mushayt [KM], Kingdom of Saudi Arabia and 302 healthy subjects attending the Roda Health Clinic in Abu Dhabi [AD], United Arab Emirates. A data collection sheet was designed by the researchers to include variables related to personal and vaccination characteristics. Data were obtained from medical records of the employees who were appointed at the AFH and attendants of the health clinic during 2006. Titers of hepatitis B surface antibody [HBsAb] >/= 10 IU/L were considered protective, while those <10 IU/L were considered non-protective. Seroconversion occurred in 89.5% of subjects in KM compared with 91.4% of subjects in AD. HBsAb seroconversion of participants from KM was significantly lower among subjects aged >40 years compared with those aged <40 years [86.4%, 92.9%, respectively, p=0.038]. Seroconversion was slightly lower among males [87.9%] than females [92.2%], slightly lower among non-Arabs [86%] than Arabs [91.8%], lower among diabetics [79.2%] than non-diabetics [90.2%] and those who had viral infections [85.2%] than those who did not have viral infections during their course of vaccination [89.8%]. HBsAb seroconversion was significantly higher among subjects whose received vaccines were less than two years old than participants whose received vaccines were more than two years old [91.8%, 82%, respectively, p=0.009]. In AD HBsAb seroconversion of participants was significantly lower among subjects aged >40 years compared with those aged <40 years [87.7%, 94.9%, respectively, p=0.026]. Seroconversion was significantly lower among males than females [88.4% and 95.4%, respectively, p=0.031], slightly lower among non-Arabs [89.8%] than Arabs [92.6%], significantly lower among diabetics [84.3%] than non-diabetics [92.8%] and among those who had viral infections [82.4%] than those who did not have viral infections during their course of vaccination [91.9%]. HBsAb seroconversion was slightly higher among subjects whose received vaccines were less than two years old than participants whose received vaccines were more than two years old [91.8% and 90.1%, respectively]. The main reason for failure to seroconvert after full course HB vaccination includes the use of vaccine lots that are more than two years old. Besides, old, male and diabetic subjects tend to have lower serconversion rates. Anti-HB vaccines should be properly stored till use. Further study is needed to decide if old [>40 years], male diabetic subjects may need more booster doses of anti-HB vaccination to achieve seroconversion