Research
Unit on Epidemiology and Information Sciences, National Institute of Health and
Medical Research (INSERM U444), Paris, France.
Hepatitis B is
one of the major vaccine-preventable communicable diseases, it is the cause of
an estimated 2 million deaths per year, and more than a third of the world’s
population shows serological evidence of past or present HBV infection.
Worldwide, it is estimated that 350 million people are chronic HBVcarriers , of
whom 170 million are in Africa and almost 30 million in Asia. These chronic
carriers have a 25% lifetime risk of dying from cirrhosis or hepatocellular
carcinoma, which account for respectively 700,000 and 300,000 deaths each year.
Areas
of particularly high endemicity include Sub-Saharan Africa, South East Asia and
the Amazon basin. In these areas, the perinatal and early childhood horizontal
routes are the most common forms of transmission. Because the risk of becoming
a chronic carrier is as high as 90% when infection occurs at birth, a notable
proportion of each birth cohort become chronic carriers following perinatal
infection. It is estimated that around 40% of infants born to HBsAg-carrier
mothers will be infected at birth, and when the mothers are also HBeAg
positive, this perinatal transmission rate could be as high as 90%. Thus, in
Asia, where the prevalence of HBeAg–carrier mothers is particularly high,
between 35 and 50% of chronic carriers were infected by their mother through
perinatal transmission.
HBV
vaccination should be initiated at birth (the first dose being given within 12
hours) for several reasons: the extremely high immunogenicity of HBV surface
antigen at birth; the good vaccine efficacy (shown to be 70-95% in the
prevention of perinatal HBV infection); the impact of newborns’ universal
immunization on the incidence of hepatocarcinoma (with a decrease of more than
75% in hepatocarcinoma incidence among children 6 to 9 years old, 15 years
after the implementation of this universal programme in Taïwan). These results
confirm the North american and European recommendations. We will show that
delaying the first vaccine dose for several weeks after birth has a “cost”: a
non-negligeable proportion of chronic carriers among every birth cohort (often
greater than the common threshold considered as leading to the implementation
of immunization programmes) which is incompatible with a significant reduction
of the incidence of chronic liver complications.