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Shortages of flu vaccine are nothing new in America, but this year’s is a whopper. Until last week, it appeared that 100 million Americans would have access to flu shots this fall. Then British authorities, concerned about quality control problems at a production plant in Liverpool, barred all further shipments by the Chiron Corp Overnight, the U.S. vaccine supply dwindled by nearly half and federal health officials found themselves making an unusual plea. Instead of beseeching us all to get vaccinated, they’re now urging most healthy people between the ages of 2 and 64 not to. “This reemphasizes the fragility of our vaccine supply,” says Dr. Martin Myers of the National Network for Immunization Information, and “the lack of redundancy in our system.”Why is such a basic health service so easily knocked out? Mainly because private companies have had little incentive to pursue it. To create a single dose of flu vaccine, a manufacturer has to grow live virus in a 2-week-old fertilized chicken egg, then crack the egg, harvest the virus and extract the proteins used to provoke an immune response. Profit margins are narrow, demand is fickle and, because each year’s flu virus is different, any leftover vaccine goes to waste. As a result, the United States now has only two major suppliers (Chiron and Ave Pasteur)—and when one of them runs into trouble, there isn’t much the other can do about it. “A vaccine maker can’t just call up and order 40 million more fertilized eggs,” says Manon Cox, of Connecticut-based Protein Sciences Corp, “there’s a whole industry that’s scheduled to produce a certain number of eggs at a certain time.”Sleeker technologies are now in the works, and experts are hoping that this year’s fiasco will speed the pace of innovation. The main challenge is to shift production from eggs into cell cultures—a medium already used to make most other vaccines. Flu vaccines are harder than most to produce this way, but several companies are now pursuing this strategy, and one culture-based product (Solvay Pharmaceuticals’ InvivaC. has been cleared for marketing in Europe.For Americans, the immediate challenge is to make the most of a limited supply. The government estimate that 95 million people still qualify for shots under the voluntary restrictions announced last weekend. That’s nearly twice the number of doses that clinics will have on hand, but only 60 million Americans seek out shots in a normal year. In fact, many experts are hoping the shortage will serve as an awareness campaign—encouraging the people who really need a flu shot to get one.1.Shortages of flu vaccine show that（）.2.The word “cleared” (Line 5, Paragraph 3) might mean（）.3.Private companies have little interest in producing flu vaccines because of（）.4.From the last paragraph we can infer that（）.5.According to the passage, which of the following is TRUE?

The person who（）this type of research deserves our praise.

He might have been killed（）the arrival of the police.

With all its advantages, the computer is by no means without its（）.

The microscope can（）the object 100 times in diameter.

（）that they may eventually reduce the amount of labor needed on construction sites by 90 percent.

My pain（）apparent the minute I walked into the room, for the first man I met asked sympathetically: “Are you feeling all right?”

Water will continue to be（）it is today—next in importance to oxygen.

（）, he does get irritated with her sometimes.

One more try,（）you will succeed.

（）that my head had cleared, my brain was also beginning to work much better.

The knee is the joint（）the thigh bone meets the large bone of the lower leg.

There is a boy student downstairs（）.

（）is known to the world, Mark Twin is a great American writer.

（）on a clear day, far from the city crowds, the mountains give him a sense of infinite.

Being in no great hurry,（）.

Billie Holiday’s reputation as a great jazz-blues singer rests on her ability（）emotional depth to her songs.

I remember（）the door before I went to bed.

It’s time（）about the traffic problem downtown.

Abraham Lincoln insisted that（）not just on mere opinion but on moral purpose.

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