Fears over the H1N1 virus circulating the globe have abated somewhat this week, as a growing number of mild cases suggest that the swine flu virus is not as deadly as initially feared. However, public-health officials caution against becoming too complacent, and the Centers for Disease Control (CDC), in Atlanta, and others are still taking steps to produce a vaccine: the flu season is just beginning in the Southern Hemisphere, where the virus could mutate to become more pathogenic. It’s also possible that the virus could prove much deadlier in a second wave around the world, as was the case for the 1918 flu, which ultimately killed millions.
The CDC is currently growing a seed stock of the H1N1 virus–the first step in making a vaccine. This stock will be distributed to vaccine manufacturers around the world, who will begin production of a vaccine once they’re given the go-ahead from the CDC. However, existing methods for making flu vaccines carry some disadvantages: they are relatively slow and require large amounts of the virus to be grown in chicken eggs. Due to limited production capacity and a limited egg supply, manufacturers would need to halt or decrease production of the seasonal flu vaccine. “This is a very inefficient system that requires a nine-month lead time,” says Ted Ross, a microbiologist at the University of Pittsburgh. “We need something more rapid with something like swine flu.”
Thanks to previous pandemic fears–largely from the avian flu, a much deadlier but less transmissible virus–alternative methods for making vaccines have received a significant boost in recent years. In 2006, for example, the U.S. Department of Health and Human Services awarded $1 billion in funding to a number of vaccine makers, including GlaxoSmithKline, Novartis, and MedImmune, to develop alternative production methods. Now, for the first time during an active pandemic, researchers and pharmaceutical companies are using these approaches to make vaccines against the current strain even before efforts have begun using traditional methods.
Novartis has already developed a vaccine for seasonal flu that is grown in cell culture, using methods similar to those employed to make biological drugs and other products; it has been approved for use in Europe. “The advantage is that cell culture can be expanded enormously,” says Andrea Gambotto, also at the University of Pittsburgh. “You can culture thousands of liters of cells, whereas there is a limited capacity to produce eggs.”The company is now using both cell-culture-based and egg-based technology to create an H1N1 vaccine. While the former is faster, cell-based manufacturing capacity is limited for this new approach, says a spokesperson for Novartis.
Despite the quick start, “it’s not clear that anything but the conventional technology will be in place in time to generate clinical vaccines that are going to be needed next year,” says Gary Nabel, director of the Vaccine Research Center at the National Institute for Allergy and Infectious Diseases (NIAID), in Baltimore. That’s because these new vaccines will need to undergo extensive animal and human testing before they can be marketed. (That process may move faster in the European Union, where cell-culture-based methods have already been approved for commercial use, than in the United States.) Still, the effort will not be wasted. Researchers see the latest flu scare as sort of a trial run for the next potential pandemic strain, which may be much more serious. “It’s more of a research exercise to see how quickly we can respond to a new strain of influenza,” says Gambotto.