By Shreeya Nanda
Immunisation against hepatitis B virus (HBV) in infants protects against the development of hepatocellular carcinoma (HCC) in not only children but also young adults, a Taiwanese study finds.
The researchers say that the results "enhance our confidence" in the ability of the universal infantile HBV immunisation programme to prevent HCC in the long term.
Using the Taiwan National Cancer and Taiwan Hepatoma Study Group registries, they identified 1509 individuals aged 6-26 years who were diagnosed with HCC between 1983 and 2011. Of these, 1343 were born prior to the initiation of the HBV vaccination programme in Taiwan in July 1984 while 166 were born after.
The incidence of HCC was significantly lower in the vaccinated than in the unvaccinated cohort, with a rate per 105 person-years of 0.23 versus 0.92 (p<0.001). And vaccination reduced the risk of developing HCC by a significant 76% (p<0.001).
The vaccination-associated reduction in HCC incidence was observed in all age groups, with significant rate ratios ranging from 0.26 for individuals aged 6-9 years to 0.42 for those in the 20-26 age group (p<0.001 for all age groups).
The team also identified an effect of birth cohort on HCC prevention. Specifically, compared with the July 1984-June 1986 birth cohort, when only infants of mothers positive for hepatitis B surface antigen were immunised, the relative risk of developing HCC was a significant 41% lower for individuals born between July 1986 and June 1992, who were all given the plasma HBV vaccine (p=0.002).
Similarly, individuals in the July 1992-2005 birth cohort - all of whom received the recombinant HBV vaccine - were a significant 73% and 54% less likely to develop HCC relative to the 1984-1986 and 1986-1992 cohorts, respectively (p<0.001 for both comparisons).
And the same effect was seen in all age groups, say Mei-Hwei Chang (National Taiwan University Hospital, Taipei) and co-investigators, except in the subgroup of 6-9 year olds born between 1984 and 1986, probably due to the small number of HCC cases.
They observe that the presence of a birth cohort effect - "most likely due to the improvement of vaccination strategies in different periods of the HBV immunization program" - allays the fears raised by the rising HCC rate ratios with age that the HCC prevention effect is not as good in young adults aged 20-26 years as in children and adolescents.
Therefore, "our long term follow-up study provides new evidence that universal HBV immunization in infants has successfully prevented liver cancer in both children and young adults", the team concludes in Gastroenterology.
Gastroenterology 2016; Advance online publication
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