科學家：兒童新冠肺炎症狀較輕是因爲常得感冒？

對新冠疫情的監測發現，兒童的發病率較低，症狀也較輕。這是爲什麼呢？科學家認爲，這可能是因爲兒童經常得感冒，免疫系統已經做好了充分準備。

Children may be protected from coronavirus because they catch so many colds, scientists have suggested.

科學家指出，兒童經常感冒可能會保護他們免受新冠病毒的傷害。

Figures from the Office for National Statistics (ONS) suggest children are just as likely to pick up the virus, but few ever develop serious disease, or even show symptoms.

英國國家統計局的數據顯示，兒童和大人一樣容易感染新冠病毒，但是發展成重症的兒童沒有多少，有些甚至沒有表現出症狀。

Now scientists have suggested that children may be resistant because their immune systems are already well primed by the common cold.

現在科學家指出，兒童對新冠病毒可能有抵抗力，因爲普通感冒已經讓他們的免疫系統做好了充分準備。

The common cold is caused by four different types of coronavirus which circulate in the community and are largely harmless. But while adults pick up a cold around two to four times a year, school age children catch an average of 12 colds annually, studies have shown.

普通感冒是由社區中流行的四種不同的冠狀病毒引起的，大部分都是無害的。但是研究顯示，成年人每年大約感冒兩到四次，學齡兒童每年平均感冒12次。

Professor Sir John Bell, Regius Professor of Medicine, University of Oxford told the House of Lords Science and Technology Select Committee, that it may allow youngsters to build up some ongoing resistance that adults do not have.

牛津大學醫藥學欽定講座教授約翰·貝爾爵士告訴上議院科學技術特別委員會說，這可能會讓兒童建立起成年人沒有的抵抗力。

“How you respond may be due to the state of your existing immunity to coronaviruses generally,” he told peers.

他告訴同行說：“你對病毒的反應可能要歸因於你對冠狀病毒羣體的現有免疫力狀況。”

“There is an interesting speculation at the moment, that suggests that many people in young or middle aged groups may have T-cells that can already see coronavirus. It may well be able to provide some protection against this pathogen when it arrives.

“現在有一種有趣的猜測，就是許多年輕人或中年人可能擁有接觸過冠狀病毒的T淋巴細胞。當人體感染冠狀病毒後，這種細胞很可能會保護人體不受病原體侵害。”

“A lot of kids get seasonal coronaviruses and it’s pretty common in our population and many will have quite a strong immunity to coronaviruses generally.

“很多孩子都會感染季節性冠狀病毒，這種病毒在我們的人口中相當普遍，許多人對冠狀病毒羣體都已擁有相當強的免疫力。”

“That is unproven, but there is evidence now for cross-reactivity at T-cell level at least, and that well might help dampen the effects of the virus when we get it.”

“這還沒有經過證實，但是現在有證據表明病毒至少在T淋巴細胞層面會發生交叉反應，這會在感染時降低病毒的危害性。”

Studies have shown that by the age of four, some 70 percent of children already have antibodies against seasonal coronavirus, which could offer important protection.

過去的研究顯示，大約70%的兒童在四歲前已經對季節性冠狀病毒擁有抗體，該抗體能提供重要的保護作用。

Professor Adrian Hayday, Chair, Department of Immunobiology, King's College London said the immune systems of young people may simply be better at reacting to new viruses.

倫敦國王學院免疫生物學部主任阿德里安·黑戴教授表示， 年輕人的免疫系統可能就是更善於應對新病毒。

“All adults past a certain age - 30 to 35 - eventually have no thymus so their T-cells work by looking at whether they have seen something before, whereas children are very good at seeing things that are completely unknown.

“所有超過一定年齡——30到35歲——的成年人最後胸腺組織都會消失，所以他們的T淋巴細胞是否發揮作用取決於他們是否感染過這種病毒，而孩子們的T淋巴細胞則非常善於應對完全陌生的病毒。”

The scientists also said that older people may suffer from immune cell ‘senescence’ where their immune cells start to shut down but are not cleared away and replaced with a working version.

科學家還表示，老年人可能遭受了免疫細胞的“老化”，他們的免疫細胞開始停工，但卻沒有被清除，也沒有能工作的免疫細胞來替代。

But Prof Bell said for most people coronavirus was not a serious illness.

但是貝爾教授說，對於大多數人而言新冠病毒不會發展成重病。

“The people who get severe disease and die, the vast majority are elderly people and when young people get this disease they tend not to suffer very much.

“發展成重症而死亡的絕大多數人都是老年人，如果年輕人感染了病毒，他們一般都不會太嚴重。”

“That might be the state of people’s immune system at different ages. 70 percent of the people who get this are completely asymptomatic, so at one end of the spectrum this is not a bad viral disease, at the other end it’s terrible.

“這可能是因爲人的免疫系統在不同年齡的狀態不一樣。感染新冠病毒的人有70%完全沒有症狀，因此從一邊來看這不是一種很糟糕的病毒性疾病，但從另一邊來看這個病非常危險。”

“The vast majority of people who get this disease don’t even know they’ve had it.”

“絕大多數感染病毒的人甚至都不知道自己已經感染上了。”