"If things go well, and we develop a full-scale production, it would be several months until the vaccine were available," the CDC today announced in a news release. "By traditional methods, it takes about six months to produce large quantities of influenza vaccine."
There are two important phrases in the CDC announcement.
The first is "if things go well." To make any vaccine, scientists first have to develop a "seed" strain of the virus that grows well in hens' eggs -- currently the only FDA-approved way to make flu vaccine. This means taking DNA from the swine flu virus and putting it into an egg-loving flu strain capable of rapid, massive growth.
That process takes about three weeks, the CDC estimates. Around-the-clock work is under way, but the virus grows only so fast.
Once the seed virus is created and sent to manufacturers, it will take them eight to 11 weeks to create small batches of flu vaccine for safety testing. If the vaccine proves safe, mass production begins.
That normally takes several months. "But influenza vaccine production is pretty unpredictable," the CDC warns.
Flu vaccine makers already are making flu vaccine for the next Northern Hemisphere flu season. Normally, vaccination begins in September.
The question is whether the CDC will ask manufacturers to switch to making swine flu vaccine -- and risk not having enough seasonal flu vaccine -- or to try to add the swine flu to the seasonal vaccine, thereby risking delay of seasonal flu vaccine.
In either case, there won't be enough flu vaccine to give to every single American -- let alone everyone in the world. So even before there's a swine flu vaccine, we'll have to face difficult decisions, CDC Acting Director Richard Besser, MD, today said at a news conference.
"We would be looking to see ... who the groups are at greatest risk for having bad outcome," Besser said. "It's less of a science decision than it is a societal decision because, clearly, we would not be able to have vaccine for 300 million people."
Faster Swine Flu Vaccine?
The second interesting phrase in the CDC announcement is "by traditional methods."
Hens can lay only so many eggs in the sterile production facilities used to make vaccine. It's a tricky process, and a lot can go wrong -- but in most years, flu production goes smoothly along its six-month time track.
If growing viruses in eggs seems old-fashioned, that's because it is. There is a faster way to grow vaccine viruses -- in cultures of human cells -- and it's already approved in Europe. Baxter International Inc. has already asked the CDC for seed virus to get production under way.