Influenza and VaccinesThere is no specific cure for influen

游客2024-01-03 46

问题 Influenza and Vaccines
There is no specific cure for influenza. Recommended treatment usually consists of bed rest and increased intake of nonalcoholic fluids until fever and other symptoms lessen in severity. Certain drugs have been found effective in lessening flu symptoms, but medical efforts aimed against the disease focus chiefly on prevention by means of vaccines that create immunity.
No drugs can cure influenza, but certain antiviral medicines can relieve flu symptoms. Available by prescription, these drugs provide modest relief, but only if taken on the first or second day of symptoms. The drugs amantadine(sold under the brand name Symmetrel)and rimantadine(Flumadine), both in pill form, work against hemagglutinin and are effective in treating type A influenza. Two other drugs inhibit neuraminidase and are effective against both type A and type B strains: oseltamivir(Tamiflu)is in pill form and zanamivir(Relenza)is an inhalant.
A flu vaccine consists of greatly weakened or dead flu viruses, or fragments of dead viruses Antigens in the vaccine stimulate the patient’s immune system to produce antibodies against the viruses If the flu viruses invade a vaccinated person at a later time, the sensitized immune system recognizes the antigens, produces the antibodies and quickly responds to help destroy them .
About 5 to 10 percent of people who receive a flu vaccine experience mild, temporary side effects, typically soreness at the injection site. Young children who have not previously been exposed to the influenza virus are most likely to experience side effects.
Flu viruses constantly change, so different virus strains must be incorporated in vaccines from one year to the next. Scientists try to provide a good match between the vaccine and the most serious virus strains circulating at the time. But because it takes months to manufacture and distribute vaccines, decisions on their composition must be made well before the start of each flu season. Each February experts at the World Health Organization(WHO)recommend a vaccine composition to be used for the forthcoming winter in the Northern Hemisphere; a second recommendation is made in September for vaccines to be used in the Southern Hemisphere. Typically vaccines contain antigens from three virus strains, usually two strains from type A and one strain from type B.
According to the CDC, the success of flu vaccines varies from one person to another. In healthy young adults, the vaccines are 70 to 90 percent effective in preventing the disease. In the elderly and people with certain chronic medical conditions, the vaccines are less effective in preventing illness but help reduce the severity of an infection and the risk of major complications or death. Studies show that flu vaccines reduce flu-related hospitalization by about 70 percent and flu-related deaths by about 85 percent among elderly people.
The CDC recommends annual flu shots for people who are at high risk for developing serious complications as a result of an influenza infection.(A)

This group includes all people aged 65 and older; people in nursing homes and other facilities that house people with chronic medical conditions; people with chronic heart, lung or kidney disease, diabetes, an impaired immune system, or severe forms of anemia; children and adolescents with conditions treated for long periods of time with aspirin(which makes them vulnerable to Reye’s syndrome); and women who will be in the second or third trimester of pregnancy during the influenza season.(B)

Some doctors encourage individuals who travel to areas of the world where influenza viruses circulate to receive the most current vaccine.(C)

Vaccination taken earlier can better protect the travellers from being infected by influenza in the epidemic areas.(D)

Vaccination is more urgently needed particularly if they are at higher risk of complications
It takes the human immune system one to two weeks after vaccination to develop antibodies to the flu antigens According to the CDC, the best time to get flu shots in the United States is between October 1st and mid-November—sufficiently in advance of the peak of influenza activity, which in the United States generally lasts from late December until early March.
Flu shots must be given annually for two reasons. First, antibody protection that is provided by the vaccine decreases during the year following vaccination. Second, vaccines created for pre-existing viral strains may not work against new strains; nor does an infection with one flu strain confer immunity to infection by another strain. [br] The word annually in Paragraph 9 is closest in meaning to______.

选项 A、at an early time
B、once every year
C、by safe means
D、at a quick speed

答案 B

解析本题为词汇题，主要考查考生根据上下文对单词annually一词的理解。在原文中，这个词是用于描述注射流感疫苗这个动作的。要判断这个词的意思，我们可以从下文中找到线索。下文的两句话是对第一句原因的解释。在解释中，作者多次用到了今年、下一年等词语。再加上前文的一些描述，如WHO每年公布疫苗的成分等，由此我们可以判断annually应该为每年一次，即B项。另外几个选项的意思都不符合原文，A项是说在更早的时候，C项是说以安全的方式，D项是说以更快的速度。

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