Vaccine Nation

For answers about an H1N1 vaccine, we turned to pediatrician and respiratory virus expert Ruth Karron, MD, director of both the Bloomberg School's Center for Immunization Research and the Johns Hopkins Vaccine Initiative. Karron is also a professor in International Health.

What’s the U.S. vaccine plan?

The U.S. government has allocated $1 billion for H1N1 vaccine development and testing. The CDC has supplied vaccine manufacturers with H1N1 “seed viruses,” and the manufacturers have begun vaccine production. Later this summer, a whirlwind of clinical trials will test new H1N1 vaccines. 

What should we expect in the fall?

The seasonal flu vaccine may be ready as early as September, says Karron, because the manufacturers want to clear the decks for production of H1N1 vaccine. “Then maybe in October, if all the stars align, the new vaccine will be ready,” she says. If a decision is made to use the H1N1 vaccine, then most children and adults under 60 would need three doses of flu vaccine—one for seasonal flu and two for the new H1N1. (This H1N1 is so novel that most people are naïve to it and will require a booster.) Adults over 60 may only need one shot of the new H1N1 vaccine; there’s data to suggest that they have some natural immunity as a result of a similar swine flu that circulated up until 1957.

Will there be enough vaccine in the fall?

If the U.S. chooses to immunize against H1N1, it is unlikely that there will be enough vaccine to immunize everyone at once. It will be necessary to prioritize based on disease epidemiology (who is most vulnerable), while maintaining essential community services.  

What makes the process so time-consuming?

The virus needed to create the vaccine is grown in eggs. Another way to grow the virus is to use cell culture technology—but it’s unlikely that we’ll see cell-based flu vaccines here this year, because cell culture-based flu vaccines are not currently licensed for use in the U.S.

Can we stretch doses?

One egg provides up to five doses of a single inactivated vaccine strain. By augmenting the vaccine with an adjuvant (an immune-boosting agent), 10 to 100 times more doses per egg could be manufactured. “But in the U.S. there is no licensed flu vaccine with adjuvant,” says Karron, “and that kind of formulation would likely require additional testing.”

Mist or shot?

Another option is to produce live attenuated vaccines. (FluMist is the live attenuated vaccine currently licensed in the U.S.)  With live attenuated vaccines, hundreds of doses per egg can be created. The drawback? Live attenuated vaccines aren’t currently used for children under age 2, asthmatics or the elderly. “There’s no one [method],” says Karron. “My hope is that we’ll use a number of strategies.”

What is our global responsibility?

“We know from previous pandemics that 90 percent of flu deaths occur in resource-poor countries,” says Karron. “We really need to pay attention to making vaccines available globally, and making them available among the poor here, as well.” One such effort underway is the donation by GlaxoSmithKline of 50 million doses of H1N1 adjuvanted flu vaccine to the WHO toward a stockpile that can be distributed to developing countries.