When Will That Flu Vaccine Be Ready?

Despite recent news report to the contrary, the U.S. Centers for Disease Control and Prevention (CDC) assures ScienceInsider that efforts to make a vaccine against the virus causing the swine flu outbreak have not met unexpected delays.

Confusion about the vaccine timeline stems from a report from the World Health Organization (WHO) yesterday, which recounted a meeting held by a scientific working group that looked closely at the production issues. The advisory working group concluded that manufacturers would not be able to begin “large-scale production” of a vaccine against the novel H1N1 virus until mid-July. The report did not describe these as delays, but many media accounts did, noting that WHO’s Marie-Paule Kieny, director of WHO’s initiative for vaccine research, earlier predicted that production could begin 2 months earlier and suggested that a vaccine might be ready as early as September.

Tom Skinner, a spokesperson for CDC, assured ScienceInsider that everything is on track. “We’re hopeful we can have a vaccine ready by late fall; however, we know that the manufacturing process is complicated, and we need to be prepared in case we run into glitches with production of the vaccine,” says Skinner. The timing, of course, depends on the specific steps in the manufacturing process, and CDC and the WHO working group appear to have different estimates on some key points.

The vaccine process begins with the viral isolate being converted into “seed stock.” CDC has already sent five isolates to seven laboratories to make this starting material. A key property of seed stock is that it’s a weakened, or attenuated, version of the original virus, which makes for a safer production process and lowers the risk of an accidental release.

Skinner says CDC expects to have the seed stock in hand next week. According to the WHO report, it will then take 1 to 2 weeks of testing in animals to make sure that the seed stock is properly attenuated. But Skinner says CDC will simultaneously conduct these animal tests and send the seed stock to some manufacturers that have biosafety level 3-plus laboratories (BSL-3 plus), which are specially designed to work with dangerous pathogens. “Those that have the BSL-3 plus labs, and some do, will start right away,” says Skinner, who stresses that, in the United States, all of this depends on the government deciding to procure the vaccine, which has not happened yet.

The WHO report says that manufacturers then typically need 1 to 2 months “to isolate rapid growing strains to maximum yield.” Skinner says not so. “They have to do a little more work on it to get it in the condition that they need for the vaccine, and I’m told that takes a couple of weeks, so that by the middle of June toward the end of June, they could start producing pilot lots,” he says. These pilot lots are used in small clinical trials to make sure that the vaccine is safe and triggers the appropriate immune responses, a process that Skinner says takes about 8 weeks.

But Skinner stresses that manufacturers do not normally put production of commercial lots of vaccine on hold until they have results from the pilot lot tests. “They’re not going to wait until all that’s done to start producing the vaccine that the rest of us might need in fall and winter, ” says Skinner. “Those two processes are parallel.”

As to exactly when this vaccine may be ready, Skinner says that’s a question for manufacturers. A spokesperson for GlaxoSmithKline, a major maker of influenza vaccine, says, “We expect the first doses of H1N1 vaccine would be available 4 to 6 months after we receive the seed strain, pending regulatory approval.” This means the vaccine would be available in mid-October to mid-December—and that’s assuming that no manufacturing problems or unforeseen regulatory issues surface. WHO’s Kieny on 1 May estimated that it would take only 4 to 6 months to produce a vaccine from the time of viral isolation, which would mean a September availability.

Is CDC concerned that the vaccine may not be ready in time? “It’s safe to say that we’re planning with multiple scenarios in mind when a vaccine might be available,” says Skinner.

Even if the U.S. government decides to purchase vaccine, Skinner acknowledges that the country may not end up using the product if the spread of novel H1N1 doesn’t warrant it. “We’re going to be looking very carefully at what happens over the summer here in the United States, but particularly at what’s happening in the Southern Hemisphere in regard to the new H1N1, to have that information to decide what, if anything, we’re going to do in regards to a vaccination campaign later this fall and winter,” says Skinner. “But if we think we might need a vaccine, we have to move now to ensure that we have one, and that’s what we’re doing.”