Scientists are calling for changes to vaccine development after the surprise announcement that Chiron will be unable to deliver half the US flu vaccine supply. The severe shortage also suggests the government is unprepared to deal with an infectious pandemic.

Vaccines are an unprofitable venue for drug companies: the annual flu jab normally sells for $7–10, compared with $3,500 for a year's supply of Viagra. As a result, the US has only two major flu vaccine suppliers: California-based Chiron, whose manufacturing license was suspended because of sterility concerns, and French company Aventis Pasteur. “In 1955, 36 companies made vaccines. Now there are 4 or 5,” says Paul Offit, chief of infectious diseases at Children's Hospital of Philadelphia.

Vaccine prices are low in part because the government buys a large percentage of vaccines and can command low prices. But another reason is that society doesn't value these preventative medicines, says Charles Helms, chair of the National Vaccine Advisory Committee. Although people are clamoring for vaccine now, there is normally little public demand, Helms says.

In press conferences following the Chiron announcement, Julie Gerberding, director of the US Centers for Disease Control and Prevention (CDC), said that the government needs to develop long-term solutions for recurring vaccine problems. But neither the CDC nor the US Department of Health and Human Services (HHS) responded to questions about details of those plans. A 2003 Institute of Medicine report on financing vaccines recommended federal subsidies to encourage manufacturers to invest in vaccine production.

One significant obstacle in vaccine production is the lengthy and expensive manufacturing process, which makes it difficult to ramp up production in response to shortages. The traditional method uses eggs to grow the necessary viral proteins, but researchers hope to develop faster methods. “We should develop vaccines we can produce and save throughout the year, and put more effort into new research, such as the live vaccine,” says Helms.

We should develop vaccines we can produce and save throughout the year. , Charles Helms, chair of the National Vaccine Advisory Committee

In late September, the US National Institutes of Health awarded a $9.5 million grant to a Canadian firm to develop a flu vaccine based on cell culture. The HHS also announced $232 million in new biodefense contracts to develop vaccines for smallpox, plague and tularemia.

Despite these measures, the flu crisis raises concerns over how the nation would cope with other infectious emergencies, such as a bird flu that could easily spread between people.

Experts worry that a concurrent outbreak of human influenza and bird flu could create a more a virulent strain. If someone is infected with two virus strains, “gene segments from each virus can mix and match,” says Richard Webby, an infectious disease expert at St. Jude Children's Research Hospital in Tennessee.

If segments of the highly pathogenic bird flu H5N1—which is rarely passed between humans—were to mix with the human virus, it could create a new strain that is easily transmitted between people. “We're not sure it's possible, but it's a definite worry,” Webby says.

Tim Uyeki, a medical epidemiologist at the CDC, says the current flu vaccine shortage has no immediate impact in the US on risk of H5N1 because that virus is not part of the human vaccine. “But [reassortment of flu viruses] is a very concerning theoretical risk,” he says.