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Among 85 children with beta-thalassemia major and ≥5 years since primary vaccination, 23 were found to be seronegative.
Findings from a new study suggested that a single booster dose of a hepatitis B vaccine after 5 years of initial administration is adequate among children with thalassemia.
A team led by Sunil Gomber, MD, Department of Pediatrics, University College of Medical Sciences, India, evaluated seroprotection rates in children with beta-thalassemia major and compared them with age-matched healthy control. The study was conducted at a tertiary hospital over a 17-month period.
“Children with thalassemia are particularly vulnerable to hepatitis B infection not only on account for multiple transfusions but also due to immunological derangements,” Gomber and colleagues wrote.
“The long term seroprotection following hepatitis B vaccination has been reported as to vary from 13-80% in different studies and the need for booster doses remains controversial,” they indicated.
A Cross-Sectional Study: Beta-Thalassemia and HBV Vaccination
A total of 170 patients—half of which were diagnosed with beta-thalassemia (mean age, 11.4 years)—were included in the study.
The investigators excluded any children with evidence of hepatitis B infection or immunodeficiency (such as HIV).
Further, the control groups included healthy siblings of the beta-thalassemia patients as well as patients visiting the out-patient department for minor illness.
All patients, however, had received their primary Hepatitis B vaccine ≥5 years ago.
“Participants were assessed for anti-HBs titers, and those with beta-thalassemia major who were seronegative (titres<10 mIU/mL) were administered a single booster dose of hepatitis B vaccine,” the investigators explained. “CD4 counts, serum levels of IL-2 and IFN-γ, and anti-HBs titres were evaluated at baseline and following booster dose of vaccine.”
At study outset, they noted that mean time since first dose was 10.7 years in the thalassemia group and 10.9 years in the control group (P = .34).
Furthermore, mean anti-Hbs titers were higher in those with beta-thalassemia (35.90 mIU/mL) compared with those without beta-thalassemia (14.40 mIU/mL; P = .001).
As such, they noted that seroprotection rates were greater for the thalassemia patients than the controls (72.9% vs 27.1%; P = 0.007).
Among the thalassemia population, 23 children were found to lack seroprotective titers. The investigators reported that the mean time lag for these children was 11 years.
These children were then administered a booster dose of the Hepatitis B vaccine. Following roughly 4.7 weeks since administration, estimated anti-HBs titers were >10 mIU/mL for all children—rising from a mean of 5.1 mIU/mL pre-booster to a mean of 278.1 mIU/mL post-booster.
“Among the 23 seronegative children with beta-thalassemia major, CD4 counts were normal in all except two children, IL-2 was detectable in only two children and IFN-γ was undetectable in all children,” the team wrote. “Even following antigenic stimulus (HBV booster), only ten children had detectable IL-2 and five had detectable IFN- γ levels.”
Gomber and colleagues did not report any statistically significant relationship between proportion of seroprotected children and time between primary vaccination (P = 0.25).
Limitations and Conclusions
The investigators acknowledged the lack of serial annual titers that would have allowed them to determine the precise moment of decline to seronegative levels.
They also indicated a utility in comparing CD4 counts and cytokine levels in seronegative children for both groups; however, financial constraints limited their investigation.
Nevertheless, they pointed to the intact humoral response in seronegative children who received a booster vaccination, which can have implications on the treatment of those with thalassemia.
“Based on our findings and considering the increased risk of hepatitis B in children with beta-thalassemia major,” they concluded, “we suggest regular assessment of anti-HBs titers following primary hepatitis B vaccination and recommend administration of a booster dose whenever indicated at the earliest.”
The study, “Requirement of a Booster Dose of Hepatitis B Vaccine in Children With Thalassemia After 5 Years of Primary Vaccination: A Prospective Study,” was published online in Indian Pediatrics.