Experts are uncertain if it will take one or two doses of the new H1N1 vaccine to give the proper protection needed against the new swine flu.
Multiple shots may be necessary to protect against both the seasonal flu and the swine flu.
There are a number of possibilities that could also occur.
Older adults are recommended to get the available seasonal vaccine, since they are currently not on the priority list for the swine flu vaccine.
Another option would require individuals to get the regular vaccine in one arm and the swine flu vaccine in the other arm.
People could also get up to three shots -- two doses three weeks apart for the swine flu, plus the regular flu vaccine.
Children under the age of nine could get an additional shot, if they have never been vaccinated.