Health care workers lined up to be innoculated against swine flu as the United States began a massive campaign aiming to vaccinate 250 million people against the illness by year's end.

Squirt up the nose

The health care workers on the frontlines of the ambitious program will get a squirt up the nose, not a shot in the arm, as the nasal spray vaccine has rolled off production lines ahead of the injectable variety.

Swine flu vaccine

Some 600,000 doses of swine flu vaccine have been shipped out to public health authorities in 21 states and four large cities Chicago, New York, Philadelphia and Washington.

Children and health care workers are at major risk

Children and health care workers are among five groups that the Centers for Disease Control and Prevention (CDC) has recommended be given priority for the H1N1 vaccine.

Risk groups

The other at-risk groups who the CDC has recommended should be vaccinated first are pregnant women, people in contact with infants, and adults under the age of 65 with underlying medical conditions.

Many will not be able to have the nasal spray

Many will not be able to have the nasal spray vaccine as it was contraindicated for pregnant women and people with chronic medical conditions.

Vaccinations have already been administered to health workers

Vaccinations have already been administered to doctors, nurses, first responders such as firemen and other health personnel in the states of Illinois, Indiana and Tennessee, according to the Centers for Disease Control and Prevention (CDC).