Q: How much vaccine is available now?

A: According to the Centers for Disease Control and Prevention, as of Nov. 2 there were slightly more than 30 million doses of H1N1 vaccine available for states to order.

Q: Is there a shortage?

A: There's less vaccine available than companies had promised and the CDC had hoped. The original estimates were up to 40 million doses by the end of October. The 40 million doses ended up being 30 million. How many will become available by the end of the flu season is unknown.

A: What was the problem?

Q: The H1N1 virus turned out to be slow-growing and didn't yield as much as other flu strains have. The virus has to be grown out in chicken eggs, a 50-year-old technology that is "tried and true" but difficult to speed up, says the CDC's director Thomas Frieden.

Q: Is vaccination being restricted to those at highest risk?

A: The vaccine is being distributed through the states, and most sites are working on the honor system. The highest priority are pregnant women, health-care workers, people caring for children younger than 6 months old (the babies can't be vaccinated), all people between 6 months and 24 years old, and then everyone else with chronic underlying diseases such as diabetes, asthma and immune disorders. Few vaccination clinics are demanding proof that people wanting to be vaccinated fall into a high-risk category.

Q: When will there be enough for everyone to be vaccinated?

A: The CDC can't say exactly, only that more is coming. Some health departments are saying they won't be caught up, in terms of getting and delivering the vaccine, until December.

Q: What about the seasonal flu vaccine?

A: The CDC recommends that everyone get that as well, though at this point almost all the flu circulating is the H1N1 strain. There's still seasonal vaccine available, though some sites have run out. A total of 85 million doses were distributed and more than 60 million people had been vaccinated as of Oct. 23, says Frieden. That's "unprecedented," he says.