Baculovirus is the plague of the fall armyworm, which is itself a major pest for corn farmers. The virus infects the caterpillar's cells and hijacks them to produce the proteins it needs to thrive and spread. Scientists have appropriated this cellular machinery to produce other proteins, including hemagglutinin, the key used by the influenza virus to infiltrate human cells and make us sick. Now a vaccine produced from such insect-derived hemagglutinin has proved effective in preventing infection by several strains of human influenza, according to a new report in JAMA The Journal of the American Medical Association.

Vaccine clinical researcher John Treanor at the University of Rochester and his colleagues tested the new vaccine—dubbed FluBIØk by its maker Protein Sciences Corp. in Meriden, Conn.—in 460 volunteers, primarily women, in a study funded by the company. Over the course of the 2004-2005 flu season, one third of the patients received a placebo, a third received a small dose of the vaccine, and another third received a larger dose.

The vaccine proved effective, stimulating an immune response that grew stronger with higher doses without any dangerous side effects. In the months following immunization, seven in the placebo group fell ill with the flu, developing a fever of over 99.8 degrees Fahrenheit combined with either a sore throat or a cough; two from the small-dose group got sick and none of the high-dose subjects came down with symptoms. "This study shows that the vaccine using this new process protects from the flu," Treanor says, "even when the infecting strain of flu is antigenically drifted," or slightly different from the strain in the vaccine itself.

A larger study with thousands of patients will be needed to further prove efficacy, Treanor notes, but the new vaccine offers an alternative to the traditional manufacturing method: eggs. Hundreds of millions of fertilized eggs are needed each year to produce flu vaccine and this recipe cannot respond quickly to changes in the flu virus that is being fought. A particular variant flu virus must first be isolated and manipulated so that it will grow well in the eggs—a process that can take several months and does not always work. "None of that is necessary in this process. All we're interested in is the gene for the hemagglutinin," Treanor explains. "You don't have that need to tinker with things and, because of the shortcuts you can take, you could conceivably generate a vaccine faster and have it earlier in the [flu] season."

The ability to accelerate production could also prove vital in the face of a flu pandemic, shielding producers from the need to work with a pathogenic live virus. Baculovirus has already produced a vaccine for human papillomavirus, the infectious agent behind cervical cancer. But this does not mean that chicken eggs will be entirely replaced by infected caterpillar cells as vaccine makers. "I personally do not believe that this will become the exclusive way that flu vaccines are made," Treanor says. "We are going to enter an era where there are many different ways to get there."