The first human test of an experimental vaccine against a deadly strain of avian flu, using novel technology that could produce millions of doses very quickly, produced protective antibodies in the vast majority of those who received it, scientists said on November 19.
The encouraging results in the early stage trial from Novavax, a biopharmaceutical company based in Rockville, Maryland, were published online in the New England Journal of Medicine.
"These are very preliminary results, but it appears for the first time that we may have a vaccine that would work against an outbreak" of avian flu, said Robin Robinson, director of the Biomedical Advanced Research and Development Authority, or BARDA, the federal agency in charge of developing countermeasures against public health emergencies.
Because other candidate vaccines against avian flu have failed, "this is a very important milestone," he said. "We have a promising vaccine where before we had none."
The H7N9 strain of avian flu emerged in China last winter, causing 45 deaths in 137 confirmed cases this year through late October, according to the World Health Organisation. Cases and deaths, often from severe pneumonia, both peaked last March and April.
But public health experts fear the virus could come storming back this flu season. After no reported cases of H7N9 in China in August or September, there have been four since early October.
A mortality rate of one-third suggests the virus is highly lethal.
The WHO says there is currently "no indication" the virus can be transmitted from person to person, and so cannot become a pandemic. But flu strains are notorious for undergoing genetic changes, including those that make them transmissible between people.
In the clinical trial, conducted in Australia, 284 adult volunteers received two doses of either a dummy injection (placebo) or one of six formulations of the experimental vaccine - a high or low dose with or without an adjuvant, a chemical compound that turbocharges the immune system. The heart of the vaccine is two proteins, dubbed H7 and N9, that stick out from the virus and give it its name.
Apart from some redness and soreness around the injection site in some volunteers, mostly among those receiving the vaccine containing adjuvant, the vaccine had no ill effects, Novavax reported.
It produced meaningful levels of antibodies, molecules of the immune system that attack invaders. The vaccine triggered production of antibodies against the "H" protein in 81 percent of the volunteers who received the vaccine with the high level of adjuvant, and antibodies against the "N" in more than 90 percent.
The study did not expose volunteers to virus, which is considered unethical, to see if the antibody levels warded off infection.
"But these antibody levels are very likely to be protective," said Dr Louis Fries, Novavax's vice president for clinical and medical affairs, who led the study.