With school about to start next week in many parts of the U.S., and dire warnings sounded about an expected rapid spread of the H1N1 virus, public health officials appear to be struggling to put in place an effective plan to inoculate the nearly 159 million Americans at the greatest risk.

“The CDC has been working with HHS (Health and Human Services) and the states to develop plans for distributing the vaccine, but what works best for a large state or city like New York may not work best for a small state like Wyoming,” said CDC spokesman Joe Quimby. “Our first recommendation is that people contact their local health provider and that might be their local doctor’s office, or their local county health department.”

Other than doctors’ offices, where people will be able to get the forthcoming vaccine is still unclear.

Initially, the number of vaccine doses allocated per state will be based on population only – meaning the larger the population, the more doses a state will receive.

Rather than develop a completely new vaccine program, U.S. health officials will distribute the vaccine similarly to what’s done for the current children’s vaccine program, but will enhance it to enroll a larger number of providers.

But it is currently impossible to predict where the hotspots will be for H1N1 activity this fall, and whether certain places will require more vaccine than others, Quimby told FOXNews.com.

This spring, for example, major cities like New York and Chicago, and border states such as California and Texas were among the hardest hit by the virus.

As of August 15, which is the most recent period available from the CDC, only two states were reporting widespread flu activity – Maine and Alaska.

“The vaccine is going to be distributed to states on a prorated basis of population so that everybody will get the vaccine as soon as it’s available,” Quimby said.

Distributing the H1N1 Vaccine

Although public health officials initially talked of setting up public vaccination stations in communities throughout the U.S., Quimby said whether or not this happens will be decided by the states themselves.

Setting up vaccination stations at public schools is another option, but again will be left up for states and local communities to decide, Quimby said.

“There are very much a range of possibilities and a range of distribution methods, which will vary by city and state,” he added.

First Doses

The first batch of the H1N1 vaccine, expected to be around 45 million doses, is slated to arrive in mid-October and will be set aside for five target groups:

— Pregnant women who are considered 4-times more likely than the general population to experience complications from the H1N1 flu.

— People who live with and/or care for infants under the age of 6 months and children, i.e. parents, siblings, daycare providers, teachers.

— Health-care and emergency medical providers.

— Children age 6 months to adults up to the age of 24. The attack rate for children between the ages of 5 and 14 is 14 times higher than that for adults over the age of 50.

— People age 25 to 64 years old with underlying health conditions that put them at high risk for influenza complications.

People receiving the H1N1 vaccine will need two doses to build up resistance.

All Americans are encouraged to get a seasonal flu vaccine as well, Quimby said, which should already be available at their physician’s offices.

“We’re calling on people to take some personal responsibility, call your doctor and get the regular flu shot now since it’s already available,” he said.

45 Million Doses Versus 159 Million People

At least initially, there will not be enough vaccine for all the population groups recommended for immunization. Quimby said that each flu season, about 40 percent of the people that the CDC recommends for flu shots actually get them. If this holds true with H1N1, about 63.6 million people will line up for H1N1 shots this year, meaning the initial batch of vaccine will be about 18.6 million doses short.

If that is the case, the following subset will be eliminated until more vaccine becomes available, according to the government's Advisory Committee on Immunization Practices:

— People age 19 to 64 years old with underlying health conditions that put them at high risk for influenza complications.

That group will be immunized once the next batch of vaccine becomes available. Government health officials believe it will ultimately receive more than the 195 million needed doses.