H. pylori vaccine research shows promise

Yet some physicians question its value as the prevalence rate of the bacteria, closely linked to ulcers and stomach cancer, is declining in the United States.

By Victoria Stagg Elliott, AMNews staff. Feb. 10, 2003. Additional information

Several recent studies have suggested various strategies that may eventually lead to a vaccine for Helicobacter pylori, a bacterium that has been associated with everything from anxiety disorders to strokes, although it is most strongly linked to peptic ulcers and stomach cancer.

A paper published in the January issue of Infection and Immunity found that a nasal vaccine combining the killed bug with cholera toxin and nonspecific bacterial DNA provided near-complete protection in mice.

Another paper, published in Vaccine in January, found that an immune response could be generated in uninfected people who swallowed the killed bacteria combined with altered Escherichia coli. The study itself was small, though, and involved only five subjects.

At least two companies are also working toward developing the vaccine's commercial potential.

But the hunt for something that will prevent infections from a bug usually hidden in the mucosal lining of the digestive tract is tricky.

Only the most optimistic predict a vaccine in fewer than five years. Most see it as something that will come along much further into the future.

Helicobacter pylori is most often found in the mucosal lining of the digestive tract.

"It is somewhat difficult to touch a bacterium like this," said Amnon Sonnenberg, MD, a gastroenterologist with the VA Medical Center in Albuquerque, N.M. "And it's developed multiple defense mechanisms."

But for many public health experts and some physicians, the need is great.

In the Institute of Medicine report on vaccine priorities, an H. pylori vaccine made it into the second-highest priority category.

"It probably would be quite useful," said Mel Wilcox, MD, director of gastroenterology and hepatology at the University of Alabama at Birmingham. "If you could give a vaccine to children and you could prevent this infection, that would probably prevent a significant number of ulcers."

But many physicians are not so sure the vaccine would make an impact, particularly in the United States. H. pylori prevalence once approached 100% here and still does in many less-developed parts of the world, but, for the United States, it's not around as much as it once was.

"I don't think it would be very useful at all," said James Smith, MD, director of gastrointestinal endoscopy at the Ochsner Clinic Foundation in New Orleans.

When he started his career more than 15 years ago, a majority of the bleeding ulcers he treated were caused by the bug. Now, he says that number is less than 20%.

"H. pylori is becoming less and less of a problem every decade. Now, most of the ulcers are due to aspirin, ibuprofen and arthritis medicines," said Dr. Smith.

A vanishing problem?

A combination of an increase in the use of antibiotics to knock out the bug and significant improvement in hygiene has caused infection rates to plummet. According to the Centers for Disease Control and Prevention, about 50% of those older than 60 carry the bug, but only 20% of those younger than 40 do. Gastroenterologists also say that they see fewer and fewer ulcers caused by H. pylori.

"The bug is vanishing from the environment," said Dr. Sonnenberg. "The problem seems to be solving itself."

Vaccination would also have to happen during childhood, when most people pick up the infection. But most physicians aren't so sure that parents will buy into yet another injection for an adult disease that is fading anyway. Also, for the majority of people infected, it doesn't actually cause disease. If it does, there is reasonably effective treatment.

"There's no reason to think the numbers won't decrease more on their own," said Dr. Smith. "You're talking about vaccinating children, who have such a minimal risk in this day and age of getting it that there's no point. It might make sense elsewhere in the world but not here."

ADDITIONAL INFORMATION:

Susceptibility

20% of Americans younger than 40 are infected with Helicobacter pylori.
50% of Americans older than 60 are H. pylori-positive.
80% of peptic ulcers are caused by the H. pylori bacteria.
1 million hospitalizations in the United States were linked to peptic ulcers.

Source: NIH, CDC fact sheets

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