疫苗簡史

鄧夢寒

It is hard to fully appreciate how vaccines have revolutionized modern medicine. The long schedule of vaccines may seem like a hassle， and rumors about harmful effects unnerve parents. But， the fact is， vaccines have helped save millions and millions of lives. Just a few generations ago， people lived under the constant threat of deadly infectious diseases， like smallpox， polio， and hepatitis. Lets look at the greatest infectious scourges of the past 1，000 years and how vaccines have mitigated or even eradicated the danger.

Prior to the 15th Century： Infectious disease has always impacted humanity， but even as early as 1，000 years ago， there is evidence people recognized the connection between exposure and immunity. The ancient Chinese may have used pulverized smallpox scabs taken from the sick and inhaled or rubbed them onto skin to immunize themselves. This primitive form of inoculation was practiced in Africa and the Middle East too before spreading to Europe.

16th Century： Smallpox， measles， and whooping cough were terribly common in the 1500s， with outbreaks recorded around the world. Contagious diseases like these spread quickly， especially in crowded， dirty cities. Children were especially vulnerable. Records from 16th century England indicate that as many as 30% of all children died before the age of 15， likely from dysentery， scarlet fever， whooping cough， influenza， smallpox， and pneumonia.

17th Century： When Christopher Columbus discovered the Americas in 1492， he and the Europeans that followed him unwittingly brought with them smallpox， measles， whooping cough， chicken pox， bubonic plague， typhus， and malaria. The native people， with no history of these diseases and no natural resistance， died by the millions over the 150 years that followed initial contact with European explorers. An estimated 80% to 95% of the population perished. There is perhaps no more terrible an example from history to illustrate the importance of antibodies in resisting infectious disease.

18th Century： The 1700s were a watershed century for vaccine develop-ment. Europeans realized that survivors of certain infectious diseases were immune to future exposure， and began a primitive form of inoculation by intentionally infecting themselves with a disease to gain immunity.

The risk of sickness and death with this early approach was high， but it shed light on the basic principles behind immunology and enabled British doctor Edward Jenner to develop the worlds first true vaccine. In 1796， Jenner discovered that if he infected people with the related， though relatively benign， cowpox virus he could inoculate patients with far lower mortality rates.

19th Century： After Dr. Jenners discovery of “cow pox” as the first relatively safe vaccination against smallpox， knowledge of the procedure spread rapidly and became common throughout the world. Vaccine development finally made another major step forward 85 years later when Louis Pasteur identified bacteria as a major culprit behind several diseases and used this knowledge to produce the first “l(fā)ab-made” vaccination.

20th Century： At the start of the 20th century， infectious diseases like yellow fever and polio still ravaged populations in Europe and the United States. But as the century progressed， scientists built upon the immunological fundamentals discovered over the past century and developed individual vaccinations for 27 major infectious diseases. By the year 2000， centuries-old scourges like smallpox and measles were virtually eliminated from the developed world， along with yellow fever， polio and several others.

21st Century： Since 1995， five new vaccines were added to the childrens immunization schedule in the U.S.， which the CDC estimated saved thousands of lives. The pneumococcal conjugate vaccine， added in 2001， likely saved 13，000 U.S. lives from 2001 to 2008. And the rotavirus vaccination， added in 2006， is now estimated to prevent 40，000—60，000 hospitalizations yearly.

On the global scale， health organizations continue to distribute vaccines to poorer countries. Thanks to increased access to the measles vaccine internationally， the annual death toll from the disease has fallen from almost 600，000 in 2000 to just 122，000 in 2012， a reduction of 79%.

Future of Vaccines： While existing vaccines continue to be improved and distributed， the scientific community continues to work on a few difficult diseases. There is no working vaccine for HIV， malaria， or tuberculosis （there is a TB vaccine for children， but not adults）. Consequently， these diseases continue to kill millions around the world.

A new generation of cancer vaccines， designed to train the body to better fight cancer， is also in early stages of development. The scientific community believes these drugs hold great promise for addressing growing rates of cancer， now the second most common cause of death in the United States.

很難充分體會疫苗如何變革了現(xiàn)代醫(yī)學。長長的疫苗接種時間表可能看似挺麻煩，關于疫苗危害作用的謠言也使家長緊張不已。但事實上，疫苗已經挽救了無數(shù)生命。就在幾代人之前，人們還一直受到天花、小兒麻痹癥和肝炎等致命傳染性疾病的威脅。讓我們看看過去1000年最嚴重的疫病災難，看看疫苗是如何減輕甚或消除這類危害的。

15世紀以前：傳染性疾病一直危害人類，但早在1000年前就有證據(jù)表明，人們早就意識到了接觸與免疫之間的關系。古代中國人可能早已將天花病人的痂研磨成粉并將其吸入或擦在自己皮膚上來獲得免疫。這種原始的接種方式在傳到歐洲之前，也盛行于非洲和中東。

16世紀：天花、麻疹和百日咳在16世紀極為常見，世界各地都有暴發(fā)記錄。這類傳染性疾病傳播極快，尤其是在擁擠、骯臟的城市。兒童尤為易感。16世紀英格蘭的記錄顯示，多達30%的兒童在15歲前夭折，他們很可能是死于痢疾、猩紅熱、百日咳、流感、天花和肺炎。

17世紀：克里斯托弗·哥倫布1492年發(fā)現(xiàn)美洲，與此同時，他和隨后前往美洲的歐洲人不經意間也帶去了天花、麻疹、百日咳、水痘、黑死病、斑疹傷寒和瘧疾。美洲原住民由于沒有得過這些疾病也沒有先天抵抗力，在最初接觸這些歐洲探險者后的150年中，有數(shù)百萬人死去。據(jù)估計，80%到95%的原住民人口消失了。歷史上或許沒有比這更可怕的例子證明抗體在對抗傳染病過程中的重要性了。

18世紀：18世紀是疫苗發(fā)展的轉折點。歐洲人發(fā)現(xiàn)，某些傳染病的幸存者在未來接觸這種疾病時具有了免疫力，于是他們開始進行一種原始的接種，通過刻意使自身感染疾病來獲得免疫。

這種早期嘗試的致病和致死風險很高，卻揭示了免疫學的基本原理并使英國醫(yī)生愛德華·詹納得以研制出世界上第一支真正的疫苗。1796年，詹納發(fā)現(xiàn)，當他使人們感染與天花病毒相近但相對無害的牛痘病毒后，接種病人死亡率大幅降低。

19世紀：詹納醫(yī)生發(fā)現(xiàn)的“牛痘”成為對抗天花的第一種相對安全的疫苗。施種步驟隨后迅速傳播，成為全世界普遍的接種方式。 85年后，疫苗發(fā)展終于又跨越了重要一步，路易·巴斯德發(fā)現(xiàn)了細菌是導致多種疾病的罪魁禍首，他運用這一知識研制了第一支“實驗室制造”的疫苗。

20世紀：20世紀初，歐洲和美國仍然有大量人口受到黃熱病和小兒麻痹癥等傳染病的侵害。不過，隨著時間推移，科學家基于19世紀發(fā)現(xiàn)的免疫學原理，研制出分別針對27種主要傳染病的疫苗。截至2000年，像天花和麻疹這樣古老的疫病以及黃熱病、小兒麻痹癥和幾種其他傳染病在發(fā)達國家?guī)缀蹁N聲匿跡。

21世紀：1995年以來，美國兒童的疫苗計劃中又增加了5種新疫苗——根據(jù)美國疾病控制與預防中心的估算，這些新疫苗挽救了成千上萬的生命。2001年新增的肺炎雙球菌疫苗很可能在2001年至2008年間挽救了1.3萬美國人。2006年新增的輪狀病毒疫苗目前估計每年可使4萬到6萬人免于住院治療。

在全球范圍內，衛(wèi)生組織持續(xù)為貧困國家分發(fā)疫苗。由于全世界越來越多的地方可以接種麻疹疫苗，每年死于該病的人數(shù)從2000年近60萬降至2012年僅12.2萬，下降了79%。

未來的疫苗：在現(xiàn)有疫苗不斷改進和推廣的同時，科學界也在繼續(xù)研究針對一些頑疾的疫苗。現(xiàn)在還沒有對艾滋病、瘧疾或肺結核有效的疫苗（有針對兒童的肺結核疫苗，但成人不適用）。因此，現(xiàn)在全球仍有數(shù)百萬人死于這些疾病。

新一代的各類癌癥疫苗旨在訓練身體更好地對抗癌癥，目前也處于研發(fā)初期?？茖W界認為，在應對癌癥發(fā)病率增長方面，這些藥物具有廣闊前景。目前，癌癥是美國的第二大致命疾病。

（譯者單位：上海交通大學）