Government health officials in the US are starting to launch a massive swine flu campaign for this fall, but with possiblel complications.

The said campaign aims to vaccinate at least half the nation's population within months, but is said to be lagging, as only a third of vaccine ordered are likely to arrive at the expected mid-October time.

Officials seem to still be unsure how many shots people will need, what the correct dosage should be, and how to avoid confusion among the public.

"This is potentially the largest mass-vaccination program in human history," said Howard Markel, a professor of medical history at the University of Michigan who is advising the Centers for Disease Control and Prevention, which is spearheading the campaign.

Health officials fear that when schools reopen, the number of influenza cases could peak sharply within weeks, bringing a second wave of the new H1N1 virus. This is feared to infect many more people as most don't have any immunity against it.

However, the vaccine effort carries political risks for the Obama administration. "If the outbreak fizzles, they will be susceptible to being criticized for spending billions of dollars," said Harvey V. Fineberg, president of the National Academy of Sciences' Institute of Medicine. "On the other hand, if this outbreak is early and severe and there isn't enough vaccine, they'll be critisized for under-preparation."

Officials say they are proceeding carefully, and a final decision to move will only be made once they get results of clinical trials, which tests and determines the safety and dosing of the vaccine. But they are confident the campaign will be launched anyway, as soon as manufacturers deliver the first stocks.

But the campaign lies in the shadow of the government's terrifying 1976 effort to vaccinate against swine flu. The epidemic was controlled, but the vaccine had been given to 40 million people and was accused of causing a rare paralyzing disorder - Guillain-Barré Syndrome.

"This is an overreaction," said Barbara Loe Fisher of the National Vaccine Information Center, which opposes many vaccine policies. "There is no national security threat here. Why are we operating like this? This is not polio. This is not smallpox."

Fears and misinformation about the vaccine have been circulating, including claims that it will be compulsory. But authorities say the vaccination will be voluntary and will be used only if necessary and proven safe.

[via WashingtonPost]