LONDON - When Janet Robinson flew in from New York on a business trip this week, she added an extra, unusual appointment to her schedule - "get flu shot."

Marilyn Stamm, in London on business from New Jersey, did the same thing.

Robinson and Stamm usually get their annual flu shot at home, but this year the U.S. government has asked many Americans to skip it so that there is enough vaccine for the frail and elderly, who are most vulnerable to influenza.

About half of the U.S. flu vaccine supply is not available this year because one of the nation's two manufacturers had a bacteria contamination problem at its factory and had its license suspended Oct. 5, shortly before the batches were to be shipped.

There have been no major moves by other countries to step in to help the United States make up the shortfall. They had mostly, as they normally do, ordered just enough flu vaccine to cover their own populations but not enough to sell.

"I was rather distressed that I couldn't get one, so when we came here to England last week one of the first things we did was we had our ... secretary do some research for us," said Stamm, 53. "It's not to say you couldn't find it (at home) but you'd feel guilty doing it and a number of physicians are abiding by this criteria because of the dramatic shortage."

Even though Stamm's husband, Arthur, qualified for a flu shot in the United States because he is over 65, he wasn't able to get one.

"We've been traveling on business extensively and the limitation is so severe that the hospitals and small towns are limiting the time slots that you can go to get the injection," Marilyn Stamm said. "Where we live in Fort Lee, New Jersey, the time slot that had been set up for the 65s and over was last week while we were away."

The Stamms paid $55 for each flu shot.

Dr. Richard Dawood, medical director at the Fleet Street Travel Clinic, where the Stamms and Robinson got their shots, said a steady trickle of American visitors have walked through the door in the last few weeks since the flu vaccine crisis hit the United States.

The Stamms are taking the opportunity to get vaccinated while on business in London and some others are buying a dose or two to take back home for family members. It is unclear how widespread the trend is among Americans visiting European cities, but so far doctors have not reported that Americans are flying over specially to get the vaccination.

"It's not on a huge scale, but there are one or two coming in every day who are here anyway," said Dawood, whose clinic has a Web site called www.flujabs.org. "They aren't buying up London's supplies, but I have had one or two that have had an upsetting story. They've usually got an elderly relative that needs the shot and they ask for one or two doses to take with them."