Last Updated: 2002-12-30 16:57:42 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Vaccination may be a promising strategy for preventing re-infection with an ulcer-causing bacterium, researchers in Sweden report.

But vaccines against the ulcer bug, H. pylori, or Helicobacter pylori, caused stomach inflammation in mice, so they may need to be combined with antibiotics, according to the study's first author, Sukanya Raghavan of Goteborg University. The results of the research were published in the November issue of the journal Infection and Immunity.

Besides ulcers, infection with H. pylori can cause chronic stomach inflammation called gastritis and may increase the risk of stomach cancer. Antibiotics and drugs called proton pump inhibitors can clear the infection, but there is a need for another treatment, according to Raghavan and her colleagues. They point out that treatment can be expensive, patients do not always follow the treatment as prescribed and some strains of H. pylori have become resistant to medications.

This is where vaccines come in. Most vaccines are used to prevent infection, but "therapeutic" vaccines can be given to someone already infected to boost the immune system. Working with mice, Raghavan and her colleagues, under the leadership of senior author Dr. Ann-Mari Svennerholm, tested several types of H. pylori vaccines. Some of the vaccines contained whole versions of H. pylori that had been killed, while other so-called lysed vaccines contained only bits of dead bacteria.

Some, but not all, of the vaccines that contained whole, killed H. pylori were "highly effective" at reducing H. pylori levels, Raghavan said. The effectiveness of these vaccines varied depending on what strain of H. pylori they contained. For vaccines containing whole H. pylori to be effective, the type of strain would have to be matched to the most common types of the ulcer bug, according to Raghavan.

In contrast, the vaccines that contained only portions of the ulcer bug were effective at reducing H. pylori levels, regardless of what strain was used.

But getting rid of H. pylori was not without side effects, regardless of what type of vaccine was used. Mice experienced stomach inflammation after being vaccinated.

Raghavan noted, however, that this inflammation "was not harmful, and it could be treated by eradicating the H. pylori bacteria still remaining in the stomach with antibiotics."

The researchers propose that a strategy that includes both vaccination and eradication is the "optimal choice" for treating H. pylori infection.

"We hope that this strategy of combined vaccination and antibiotic treatment should be evaluated in humans in the near future," Raghavan said.