ScienceDaily (Sep. 27, 2006) — Researchers have achieved an effective immune response to an avian influenza vaccine with doses as low as one-quarter of the norm when they added a chemical mixture known as MF59. The research is published in the November 1 issue of Clinical Infectious Diseases, now available online.

MF 59 is an adjuvant--a substance that increases the immune system's ability to respond to a stimulus. For this research, the investigators used inactivated H9N2 influenza vaccines--not the H5N1 virus currently feared as a potential pandemic strain. However, the study does suggest that if the feared pandemic comes to be, adjuvants might be used to extend the vaccine supply. Furthermore, the authors note, H9N2 is itself a pandemic threat.

The researchers vaccinated 96 young adults who were divided into eight groups receiving different dosage levels, half of the groups with and half without the MF59 adjuvant. The volunteers were tested for antibodies at 28 days and 56 days.

"Antibody in the blood to the influenza virus that you're trying to protect against is what protects people from getting the flu," said Robert Atmar, MD, lead author of the study. "What vaccines do is cause the vaccinated person to produce antibodies in their bloodstream. The higher the antibody levels, in general, the more likely people are to be protected from getting ill or from getting infected at all.

"What we found was that when the adjuvant material was included in the vaccine--at all dosage levels--the antibody response was significantly better, and as low as one-quarter the dose worked very well. And a single dose of the adjuvanted vaccine was as good as two doses of the vaccine without the adjuvant." This suggests that adjuvants might be used to stretch a limited vaccine supply and allow vaccination of greater numbers of people.

Neither group experienced serious reactions to the vaccines. However, mild pain or swelling was more common in the adjuvant group.

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