US scientists report breakthrough over bird flu vaccine

US scientists say trials on volunteers were positive and vaccine could work against H7N9 strain, which emerged in China last winter

PUBLISHED : Friday, 15 November, 2013, 4:00am
UPDATED : Friday, 15 November, 2013, 4:00am

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 have announced.

The encouraging results in the early stage trial from Novavax, a biopharmaceutical company based in Rockville, Maryland, were published online on Wednesday 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 up until late October, according to the World Health Organisation. Cases and deaths, often from severe pneumonia, both peaked in 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 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, 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 per cent of the volunteers who received the vaccine with the high level of adjuvant, and antibodies against the "N" in more than 90 per cent.

The study did not expose volunteers to the virus, which is considered unethical. "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.

Just as important as the vaccine's apparent efficacy is how quickly it can be produced, thanks to eliminating the need to use chicken eggs as most vaccine production does. Fast manufacturing is important because a pandemic flu strain can emerge with little warning. An initial outbreak of a new flu strain is often followed by a more severe and widespread outbreak the following flu season.

That happened with the H1N1 swine flu in early 2009. Vaccine makers could not produce vaccine before H1N1's "second wave" that autumn, and the virus eventually infected an estimated 61 million people in the United States and caused some 12,000 deaths, according to the US Centres for Disease Control and Prevention.

But after scientists determined the genetic sequence of H7N9 last March, and deposited it in a public database, it took Novavax only a month to produce an experimental vaccine ready to test in animals. The human volunteers received their first doses in early July.

"Our technology let us produce vaccine in just a month and start testing it in four," said Fries.