GSK flu vaccine beats Baxter's in British study

* Shot with additive provides stronger immune response

* Findings suggest U.S. may need to change view on adjuvants

LONDON, Dec 17 (Reuters) - A head-to-head study of GlaxoSmithKline's GSK.L and Baxter's BAX.N H1N1 flu vaccines found the GSK shot produced a swifter, stronger immune response and was likely to offer better protection.

British researchers said on Friday their study also found GSK’s Pandemrix H1N1, or swine flu, vaccine, which contains a chemical booster called AS03 and known as an adjuvant, could protect most adults and young people with a single dose, but two doses might be required for older people.

The use of adjuvants, designed to boost the body’s response to a vaccine, has divided health authorities in Europe and the United States.

They were widely used in Europe last year to deal with the H1N1 swine flu pandemic. In the United States, however, health officials stuck with the standard unadjuvanted formulation used in seasonal flu vaccines -- largely due to fears that people might not trust them. [ID:nN20225492]

Karl Nicholson from the University of Leicester, who led this study, said his findings suggested adjuvanted vaccines were likely to give earlier, more effective protection.

“The work we have done clearly shows that the adjuvanted vaccine is more immunogenic,” he said in a telephone interview, adding: “That is probably likely to give earlier protection, or better protection to more people.”

Pandemrix, which is produced using chicken eggs, was selected as the standard H1N1 vaccine in Britain during the swine flu pandemic, which the World Health Organisation declared over in August this year. [ID:nLDE6790D9]

Baxter’s cell culture vaccine, Celvapan, was also used in Britain but was largely reserved for people with egg allergies.

Nicholson’s team studied 347 people at three British hospitals between October 2009 and November 2009. The participants were grouped by age -- 18 to 44 years, 45 to 64 years, and 65 years and older -- and given two doses of either Pandemrix or Celvapan, 21 days apart. Blood samples were taken before vaccination and at weekly intervals after each dose to measure changes in antibody levels.

The results, published in The Lancet Infectious Diseases journal, showed the adjuvanted vaccine induced a significantly higher immune response and achieved higher rises in antibody levels than Baxter’s whole-virus vaccine in all age groups, and this antibody effect persisted up to six months after vaccination.

Nicholson said that because the H1N1 flu pandemic had been a relatively mild strain, the U.S. decision to avoid adjuvanted vaccines had not proved too risky. But he warned that may not be the case in future -- particularly if more dangerous flu strains were involved.

“If this was a pandemic of H5 or H7 influenza, or an Avian subtype, the type of vaccines...traditionally used in the United States would not really be able engender a sufficiently strong immune response to give significant levels of protection in the population,” he said. “As it was an H1 pandemic, and the globe is extremely fortunate for that.

“All the work that has been done shows that the conventional (non-adjuvanted) vaccines are really just not good enough at giving good antibody responses.”

The scientist said the AS03 adjuvant GSK uses in Pandemrix is very similar to a Novartis NOVN.VX additive called MF59, which the Swiss drugmaker used in its European flu vaccines and which has been shown in previous studies to boost and broaden protection levels against flu. [ID:nN20170594]