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THE realisation that hepatitis B vaccines protect people for longer than
previously thought may help slash the million-a-year death toll caused by the
liver virus.

Researchers have found that the immune system鈥檚 ability to 鈥渞emember鈥�
hepatitis B vaccination has been seriously underestimated. This means that fewer
doses of the relatively expensive vaccine might be needed to protect susceptible
people from infection鈥攁 major step forward for developing countries, who
should be able to afford to vaccinate more people as a result.

Hepatitis B vaccine is usually given as three shots over six months. Some
countries also give booster shots to maintain immunity in vulnerable groups such
as healthcare workers. But leading hepatitis B expert Jangu Banatvala of the
John Radcliffe Hospital in Oxford and his colleagues say that boosters are
unnecessary for people who have healthy immune systems. Their review of the
evidence also suggests that the number of initial shots could be cut from from
three to two.

A person鈥檚 immunity to a disease is usually gauged by measuring the level of
protective antibodies in their blood. However, this doesn鈥檛 tell the whole
story, says Banatvala. A person鈥檚 T and B cells remember that they have
encountered a particular infection. Researchers have recently found that even if
no antibodies to hepatitis B can be detected, these 鈥渕emory鈥� cells lurk around
the body for years and protect against the disease.

Generating a strong initial immune response is key to generating this
long-lasting memory, says Banatvala. 鈥淲hat you want is a potent vaccine, then
you don鈥檛 have to worry about booster doses,鈥� he says. Further research is
needed to see whether two doses will generate enough immune memory to give
lifetime protection, he adds.

More than 2 billion people living throughout the world have caught hepatitis
B, which is transmitted through contact with body fluids. Most people infected
as adults shake off the virus. But some, around 5 per cent, become chronically
infected, and usually develop cirrhosis or fatal liver cancer. The virus is a
leading cause of death in developing countries, killing about a million people
each year. Babies are particularly vulnerable鈥攗p to 90 per cent of those
who catch the virus from their mothers during birth become carriers.

But the price of the vaccine is a huge difficulty for these countries. 鈥淎
major barrier of new vaccines is the cost,鈥� says Jay Wenger, a hepatitis B
expert at the WHO in Geneva. The WHO is trying to implement a universal infant
vaccination programme.

Hepatitis B vaccine doubles the cost of each child鈥檚 set of shots. The price
is a significant obstacle to efforts by the WHO to introduce it globally. If
Banatvala is right, the price of a set of shots would fall significantly.

But Felicity Cutts, a vaccine expert at the London School of Hygiene and
Tropical Medicine is more cautious. 鈥淪ome people believe there is a need for
further study,鈥� she says. And Banatvala notes that for people with weakened
immune systems, booster doses might still be needed.

But for the millions at risk from deadly hepatitis B, it鈥檚 an important step
in the right direction.