The unexpected spring break is over! With swine flu apparently not as deadly as first feared, the CDC cleared schools to re-open on Wednesday. Still, health officials fear this new H1N1 virus could still wreak havoc during the regular flu season.

"We could see the current strain fizzle out and never come back. It could come back as it is or it could mutate and change into a more severe form," said Dr. Richard Besser of the Centers for Disease Control and Prevention.

That could mean you'd need up to three flu shots next fall: one for the regular flu and, depending on what tests show, up to two doses of a new swine flu vaccine.

"The number of doses you need will impact how many people you can vaccinate," said Besser.

There's a time crunch to decide whether to make this new vaccine because it takes four to six months.

"The very earliest stages of that process has already begun," said Dr. Anthony Fauci of the National Institute of Allergy and Infectious Diseases.

Health authorities are considering a number of factors, including how many doses of the regular vaccine are ready to go now; whether they can afford to switch production; hw much swine flu vaccine can be made; and who should get it first.

Dr. Marle-Paule Kleny, director of the Initiative for Vaccine Research answered those questions with more questions.

"We don't know: Is it still the older people who will be most affected? Is it the people with underlying health conditions? Is it the very young? Is it everybody?" said Kleny.

The World Health Organization could make its recommendation next week on whether to mass produce a vaccine for swine flu. The biggest manufacturers have contracts that guarantee large amounts of vaccine to certain countries first. Health authorities are trying to figure out who's covered, who's not.