(This article was #12 in Discover Magazine’s top 100 stories of 2007.)

Although avian flu made few headlines in 2007, the virus continued to claim lives in Asia, particularly in Indonesia. The good news is that this year the FDA approved the first bird flu vaccine and announced plans to stockpile it for emergency use during a crisis.

The H5N1 strain of bird flu first appeared in Hong Kong in 1997 and since then has infected more than 330 people, killing more than 200. In 2007, the virus—which normally infects birds and occasionally jumps from birds to humans—affected seven countries, prompting experts to warn that it could gain the ability to jump from person to person and trigger a pandemic.

In April, the FDA approved a two-shot vaccine made by Sanofi Pasteur. In a clinical trial, this vaccine protected 45 percent of the adults who received the highest dose against infection from H5N1. The government said its goal was to stockpile enough doses of the Sanofi vaccine to protect 20 million people as a stopgap measure until a more potent vaccine is available.

The year 2007 also brought an innovation that could significantly speed up ordinary flu vaccine production. In the conventional method, the virus is grown in fertilized hens’ eggs, which can take up to six months. John Treanor, professor of medicine at the University of Rochester, and researchers at Connecticut-based Protein Sciences instead infected caterpillar cells with an insect virus—a baculovirus engineered to produce flu virus protein from three ordinary flu strains. In a preliminary study published in the April Journal of the American Medical Association, the researchers found that the vaccine produced by this method protects against the two strains to which the subjects were exposed and most likely protects against the third. The same method could be used to create vaccines for all flu strains at least a month faster than at present.

In the meantime, Canada saw an outbreak of another deadly bird flu strain—H7N3—in September. “We can’t afford not to be concerned,” says Robert Webster, a leading bird flu expert at St. Jude Children’s Research Hospital in Memphis, Tennessee. “If you’re a chicken farmer, there’s always a pandemic going on.”