Oct. 7 (Bloomberg) -- Vaccine prepared for the 2008-2009 flu season may provide some protection against the pandemic H1N1 virus and help fend off the most severe forms of the disease, research published in the British Medical Journal found.

Of the 179 unvaccinated people in the Mexican study, 29 percent became infected with pandemic H1N1 virus, compared with just 13 percent of vaccinated patients. None of the swine flu patients who received the shot died, compared with 30 percent of those who were unvaccinated, the researchers found.

Vaccines prepared for the seasonal flu include an H1N1 strain. The shot may provide some protection against swine flu because people who have been previously exposed to a similar virus have a heightened antibody response, said researchers led by Jose Luis Valdespino at the Laboratorios de Biologicos y Reactivos de Mexico. The study was limited by the number of patients and more research is needed, they said.

“The results are to be considered cautiously and in no way indicate that seasonal vaccine should replace vaccination against pandemic influenza A/H1N1 2009,” Valdespino said in the study.

A study published in the journal Eurosurveillance in August looked at patients who tested positive for swine flu and their vaccination history and found no evidence of “significant protection” from the seasonal shot in any age group.

Valdespino’s team studied 60 patients diagnosed with swine flu and 180 uninfected people. They found that those without the disease were significantly more likely to have been vaccinated.

‘Restricted Protection’

There may be some biases with the study because it was retrospective and involved only 240 people, said Menno de Jong, head of microbiology at the University of Amsterdam’s Academic Medical Center, who wrote an accompanying editorial on pandemic vaccination.

“It suggests that if you were vaccinated, it might mitigate the disease” by boosting the immune response, de Jong said in a telephone interview. “It’s a restricted level of protection, though, and highlights the need for a specific vaccine against the novel H1N1 virus.”

Companies including Novartis AG and Sanofi-Aventis SA have produced flu vaccine to specifically target the new H1N1 strain.

H1N1 has infected at least 340,000 people and killed at least 4,100 globally as of Sept. 27, the World Health Organization said last week. The figures are based on laboratory-confirmed cases reported to the Geneva-based United Nations agency.

The researchers received funding from the Mexican Ministry of Health.

To contact the reporter on this story: Carey Sargent in Geneva at Csargent3@bloomberg.net

Last Updated: October 6, 2009 19:01 EDT