WASHINGTON (Reuters) - A vaccine additive made by Novartis and used in its European influenza shots can boost the body's immune response to a wide range of viruses, U.S. researchers reported on Wednesday.

Tests in the laboratory suggested the so-called adjuvant, called MF59, helped the immune system counteract not only the H5N1 virus in the current experimental bird flu vaccine, but mutant viruses as well.

The U.S. Food and Drug Administration study, published in the journal Science Translational Medicine, suggests using vaccines with adjuvants may protect patients against even more types of flu viruses than they are being vaccinated against.

MF59 adjuvant improves the immune response to a H5N1 vaccine by inducing qualitative and quantitative expansion of the antibody repertoires with protective potential, Hana Golding of the U.S. Food and Drug Administration and colleagues wrote.

Adjuvants, often as simple as an oil and water mixture, broaden the body's response to a vaccine, reducing the amount of active ingredient called antigen needed.

Influenza viruses are highly mutation-prone and people must be vaccinated against the particular strains circulating. This year, governments and companies had to formulate new vaccines against the new pandemic H1N1 swine flu and give them alongside vaccines for seasonal influenza.

And seasonal influenza immunizations must be reformulated every year because the viruses drift, or mutate slightly.

Researchers are also testing vaccines against H5N1 bird flu, which has only infected a few hundred people but which doctors fear could cause a new pandemic.

Swine flu has killed at least 14,000 people globally and while it is on the wane, health officials are still urging people to be vaccinated against it in case it mutates and comes back in a more deadly form.

Adjuvants are widely used in European flu vaccines as well as in Canada. But are not widely used in the United States -- even though the federal government has spent nearly $700 million buying them.

The reason? People might not trust them.

Other studies have shown adjuvants can stretch the supply of flu vaccine, because shots using them require much less of the actual vaccine antigen.

Adjuvanted vaccines produce higher immune response than unadjuvanted vaccines particularly in the elderly and young children, Dr. Vas Narasimhan, president of Novartis Vaccines USA, told a U.S. Congressional hearing last November.

The National Institute of Allergy and Infectious Diseases has awarded $60 million to researchers and companies to develop new adjuvants.

(Editing by Todd Eastham)

Canada Medicine