President Bush told senior citizens in Florida on Tuesday he was doing everything possible to ensure they get flu shots and his campaign accused Sen. John Kerry of using “scare tactics” over the vaccine shortage to win votes.

Kerry, the Democratic presidential nominee, warned a rally in this crucial battleground state on Monday that under Bush’s plan, “you don’t have a prayer of getting a flu shot.”

The vaccine shortage crisis arose when the closure of a Chiron Corp. plant in Britain cost the United States half its anticipated flu-shot supply for this year.

Two weeks before Election Day, Bush began a bus tour here focusing on domestic issues like the flu and health care and also reviving his criticism of Kerry on the war on terror.

“I know there are some here who are worried about the flu season,” Bush told a rally at a baseball park here.

“I want to assure them that our government is doing everything possible to help older Americans and children to get their shots,” Bush said, adding that millions of vaccine doses were on hand for those who need them the most and more was being rushed in.

U.S. health officials have said that only the highest-risk Americans - such as those over 65, those with chronic illnesses and babies - should get vaccinated.

In addition to raising the issue on the campaign trail, Kerry, a Massachusetts senator, has released a campaign television advertisement highlighting the vaccine crisis and blaming Bush’s policies.

Democrats say the administration failed to heed warnings that a crisis was brewing and should have done more to encourage more companies to make the vaccine and to streamline federal approval for vaccines.

Bush has blamed the vaccine shortage in part on lawsuits, a common theme as he talks about health policy.

The president’s top political strategist, Karl Rove, said Kerry was using the flu vaccine shortage as a scare tactic in Florida and that Bush’s comments were to reassure seniors.

“It’s yet an other stretch by Kerry and it’s important to say these things in a reassuring tone,” Rove said.

On the issue of national security, Bush ran down a long list of weapons systems he said Kerry opposed.

“He has a 20-year history of weakness,” Bush said, contending Kerry was “not prepared and equipped” to be commander in chief.

Florida opened early voting on Monday, allowing people to cast ballots at a limited number of polling stations in advance of the Nov. 2 Election Day. Bush was declared the winner in Florida by 537 votes in the 2000 race after the intervention of the U.S. Supreme Court halted a recount.

Bush focused on Tuesday on the middle swathe of the state, which is seen as a bellwether region. Campaigning with him was Mel Martinez, his former housing secretary, who is vying for a Senate seat held by retiring Democratic Sen. Bob Graham.

Bush and Kerry were deadlocked at 45 percent each in a Reuters/Zogby poll on Tuesday. (Additional reporting by Adam Entous)