Government health officials said Tuesday that they were "looking intently" at developing a swine flu vaccine.
"It will be a matter of deciding not to make a vaccine rather than deciding to move forward," said Dr. Richard Besser, acting director of the Centers for Disease Control and Prevention.
But undertaking work on a vaccine would be challenging. In a typical year, formulating the nation's flu vaccine is a tricky proposition.
This is not a typical year.
As they contemplate the best way to protect the public from a possible pandemic, there are decisions to be made that could complicate the annual influenza vaccine campaign.
Should they reconfigure the seasonal flu vaccine that's already under development for the fall? Or should they order up a second vaccine tailored to the new virus and trust people to take both shots?
Either option entails added expense, logistical headaches and no small measure of risk.
And since it takes about six months to produce the millions of flu shots that Americans will need in the fall, nobody can afford to wait.
The vaccine is made by growing samples of flu virus inside fertilized chicken eggs, then breaking out the key proteins that provoke an immune response. Then they are purified, tested and packaged into syringes for distribution around the country.
In February, a government advisory committee selected three flu viruses for this year's vaccine, based on surveillance data indicating which strains are most likely to be circulating in the fall and winter and causing disease.
They chose an H1N1 strain called A/Brisbane/59/2007; an H3N2 strain called A/Brisbane/10/2007; and a strain known as B/Brisbane/60/2008.
Now that swine flu is on the scene, Besser said, it could be swapped for one of the other strains or added as a fourth.
Adding a fourth "is an attractive approach in that you would have one vaccine that would cover not just seasonal flu but this new strain that is circulating," Besser said.
But such a decision won't be easy, said Dr. Wayne Marasco, an infectious disease physician and virologist at Harvard Medical School.
Using a vaccine with four viruses instead of three "would probably change the cost of production, the time of production, and the packaging that goes with it," he said.
