疫苗知识问答
2010年高考英语作者：***
来源：《英语世界》2020年第09期
Vaccines are one of our most effective health interventions， but are often misunderstood. In this Q&A， we explain what they are， how they work and why they are important.
What is a vaccine？
We’re protected from infectious dia by our immune system， which destroys dia-causing germs—also known as pathogens—when they invade the body. If our immune system isn’t quick or strong enough to prevent pathogens taking hold， then we get ill.
十一月英语 We u vaccines to stop this from happening. A vaccine provides a controlled exposur
e to a pathogen， training and strengthening the immune system so it can fight that dia quickly and effectively in future. By imitating an infection， the vaccine protects us against the real thing.新品牌如何推广
Why are vaccines important？
They protect us from dangerous dias. In some regions or populations， dangerous dias are constantly prent （endemic）. Examples include hepatitis B， cholera and polio. So long as the dias are around， we need vaccines to bolster1 our immune systems and protect us from harm.
They protect children and the elderly. Our immune systems are strongest in adulthood， meaning that young children and the elderly are particularly susceptible2 to dangerous infections. By strengthening our immune systems early and late on in life， vaccines bypass this risk.
call的过去式 They protect the vulnerable. If enough of a population is vaccinated， infections can’athena
t spread from person to person， which means that everyone has a high level of protection—even tho who don’t have immunity. This is known as herd protection （or herd immunity）. It’s important becau not everyone can be directly protected with vaccines—some people are unresponsive to them or have allergies or health conditions that prevent them from taking them.
取代英语
They can help us control epidemics. In a world of denr cities， incread international travel， migration and ecological change， the ability of emerging infectious dias （such as Ebola） to spread and cau devastation is increasing. Vaccines can be a key tool in managing this threat—but only if we have them ready for dias when they appear.customvalidator
They can help limit drug resistance. Medicine relies on being able to treat infectious dias with antimicrobial3 drugs， such as antibiotics， but overu and misu of the drugs is leading to infections becoming resistant to them. By preventing infections that would require drug treatments， vaccines reduce the opportunity for drug resistance to develop.
They are our most effective health intervention. Vaccines prevent an estimated 2–3 million deaths worldwide every year. But， a further 1.5 million lives could be saved annually with better global vaccine coverage.
How does a vaccine work？
Our immune system fights dia by distinguishing between things that belong in our bodies and things that don’t， destroying the latter. Unwanted foreign substances are identified by markers on their surface called antigens.
烟雾弥漫的意思 A vaccine works by exposing the immune system to the antigens from a pathogen， something such as a virus or bacterium that caus a certain dia. When your immune cells encounter the antigens， they mount a respon. One cell type—B cells—start making antibodies， which bind to the foreign substance， disable it and mark it for destruction. Other immune cells， known as T cells， attack and destroy cells of the body that have been infected by the pathogen.
At the same time， the body also produces long-lived types of white blood cell—called memory T cells and memory B cells—that remember the antigens that have just been encountered. If your immune system comes across the same antigens again， the memory cells allow you to mount a strong respon against that specific pathogen very quickly， so you are much less likely to get ill.
寻找幸福 Who decides who should be vaccinated？
Countries t their own vaccine policies， and so the vary around the world， with some countries choosing to make certain vaccines mandatory4.
Slovenia， for example， requires that all children are vaccinated against nine key dias before they start school. Exemption is allowed only for medical reasons， and parents that don’t comply are fined.
On the other hand， a number of other European countries， as well as Australia and Canada， have no mandatory vaccinations. Here， parents or （if old enough） individuals themlves decide.
However， the governments of such countries may offer incentives to make sure that vaccination levels remain high. In Australia， for example， parents receive certain child benefits from the government only if their child has had all of its routine vaccinations.
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