The targeted shipments come as health officials struggle to ensure the people who most need flu shots get them, now that the nation's supply of influenza vaccine has been slashed in half.

Under the plan announced today by the Centers for Disease Control and Prevention, Aventis will direct shipments of its remaining 22.4 million doses to health workers who care for patients that the CDC deems at highest risk of death or hospitalization from influenza.

The first of the shipments, about 14.2 million doses, begins immediately but will take six to eight weeks to distribute.

The CDC last week urged healthy adults to avoid getting flu shots, after British regulators unexpectedly shut down a major U.S. supplier, Chiron Corp., and halted shipment of 46 million to 48 million doses.

The CDC hopes the new plan for allocating the rest of Aventis' supply can better target the shots to the highest-priority patients: babies and toddlers ages 6 months to 23 months; anyone 65 or older; anyone with chronic medical conditions such as heart or lung disease; pregnant women; residents of long-term care facilities; children on chronic aspirin therapy; health workers who care for high-risk patients; and caregivers and household contacts of babies under age 6 months.

Health officials in Hawai'i are surveying healthcare providers to determine how many doses of the flu vaccine are still available, how many have been given and seeking estimates of how many high-risk individuals still need shots.