文章来源:未知 文章作者:meng 发布时间:2010-07-30 00:31 字体: [ ]  进入论坛

Public immunization(免疫) efforts may be much more sensitive than previously1 realized to small changes in the perceived(感官的) costs or risks of vaccination2, scientists at Harvard University report this week. In some cases, the spread of vaccine3 avoidance via social networks can make the difference between a minor4, localized outbreak and an epidemic5 four times as large. The finding, published in Proceedings6 of the Royal Society B, comes amidst one of the worst pertussis(百日咳) outbreaks in 50 years, in which 1,500 Californians have contracted whooping7 cough(百日咳) . Public health officials have cited reduced vigilance(警戒,警觉) in vaccinating8 against the disease, which sickens 90 percent of those exposed to it.

"People sometimes say that voluntary vaccination is doomed9 to fail because of the 'free-rider' problem, in which people assume they will be protected by other people's immunity10," says co-author Daniel I. Rosenbloom, a graduate student in Harvard's Program for Evolutionary11 Dynamics12, led by Martin A. Nowak. "We find that's not true, as a population of self-interested people can defeat an epidemic. But the trouble is, success is sensitive to small changes in perception of a vaccine's costs -- in terms of money, time, inconvenience, or perceived side effects."

Together with lead author Feng Fu, Rosenbloom and Nowak are the first researchers to incorporate epidemiological data into modeling of how vaccination spreads by imitation in a social network. They found that increasing vaccination cost prompts more free-riding and leads to larger epidemics13.

"Herd14 immunity in a social network is fragile," says Fu, a postdoctoral researcher in mathematical biology at Harvard. "As public perceptions of vaccine side effects change, a population can rapidly switch from high vaccination and herd(兽群) immunity to low vaccination and a larger epidemic."

The good news, the authors say, is that the sensitivity of vaccination to perceived costs cuts both ways, meaning it's easy to get a population back on track with voluntary immunizations in the wake of an outbreak.

The Harvard team found epidemics are amplified15(放大的,扩充的) when individuals mimic16 others in their social network, such as by avoiding immunizations during vaccine scares. Behavior driven by "strong imitation" -- reliance on anecdotal(轶事的) information from social contacts in deciding whether or not to immunize -- could cause up to a 14 percent decline in vaccination rates, and a four-fold increase in the size of a flulike epidemic.

"It's possible to be too clever for your own good in dealing17 with risk," Fu says. "These 'strong imitators' chase unwise risks, and their behavior exacerbates18(加剧,恶化) the fragility of herd immunity, causing it to break down more easily. Those in our model who ignored friends' outcomes and stuck with their own decision ended up better off, on average."

Fu, Rosenbloom, and Nowak's modeling also showed that in an epidemic, individuals who are hubs(枢纽,中心) in a social network are likelier to choose vaccination than their less connected peers. However, this outcome emerges primarily from self-interested behavior -- the desire to avoid sickness -- rather than altruistic19 behavior(利他行为) to protect friends and family.

"Altruistic behavior could certainly lead to increased vaccination of hubs, but we find that it's not required -- self-interested behavior suffices,"
Rosenbloom says.

This work builds upon the tradition of evolutionary game theory, where researchers construct simple mathematical models to explore human behavior in social dilemmas20 and scenarios21 where people can cooperate for the common good. While this study specifically modeled influenza22, the results apply to a wide variety of diseases, and are consistent with(与……一致) data from past epidemics.


1 previously bkzzzC     
  • The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
  • Let me digress for a moment and explain what had happened previously.让我岔开一会儿,解释原先发生了什么。
2 vaccination bKGzM     
  • Vaccination is a preventive against smallpox.种痘是预防天花的方法。
  • Doctors suggest getting a tetanus vaccination every ten years.医生建议每十年注射一次破伤风疫苗。
3 vaccine Ki1wv     
  • The polio vaccine has saved millions of lives.脊髓灰质炎疫苗挽救了数以百万计的生命。
  • She takes a vaccine against influenza every fall.她每年秋季接种流感疫苗。
4 minor e7fzR     
  • The young actor was given a minor part in the new play.年轻的男演员在这出新戏里被分派担任一个小角色。
  • I gave him a minor share of my wealth.我把小部分财产给了他。
5 epidemic 5iTzz     
  • That kind of epidemic disease has long been stamped out.那种传染病早已绝迹。
  • The authorities tried to localise the epidemic.当局试图把流行病限制在局部范围。
6 proceedings Wk2zvX     
  • He was released on bail pending committal proceedings. 他交保获释正在候审。
  • to initiate legal proceedings against sb 对某人提起诉讼
7 whooping 3b8fa61ef7ccd46b156de6bf873a9395     
  • Whooping cough is very prevalent just now. 百日咳正在广泛流行。
  • Have you had your child vaccinated against whooping cough? 你给你的孩子打过百日咳疫苗了吗?
8 vaccinating 3c0d2084d9b99d5ef019f89c134247c7     
给…接种疫苗( vaccinate的现在分词 ); 注射疫苗,接种疫苗
  • At first blush, vaccinating the wolves against rabies seems a simple solution. 乍一看来,为狼群注射防狂犬病疫苗是一种简单的办法。
  • Also vaccinating children against misers (measles) has saved many lives. 还有,给儿童进行疫苗接种防止麻疹也挽救了许多生命。
9 doomed EuuzC1     
  • The court doomed the accused to a long term of imprisonment. 法庭判处被告长期监禁。
  • A country ruled by an iron hand is doomed to suffer. 被铁腕人物统治的国家定会遭受不幸的。
10 immunity dygyQ     
  • The law gives public schools immunity from taxation.法律免除公立学校的纳税义务。
  • He claims diplomatic immunity to avoid being arrested.他要求外交豁免以便避免被捕。
11 evolutionary Ctqz7m     
  • Life has its own evolutionary process.生命有其自身的进化过程。
  • These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。
12 dynamics NuSzQq     
  • In order to succeed,you must master complicated knowledge of dynamics.要取得胜利,你必须掌握很复杂的动力学知识。
  • Dynamics is a discipline that cannot be mastered without extensive practice.动力学是一门不做大量习题就不能掌握的学科。
13 epidemics 4taziV     
  • Reliance upon natural epidemics may be both time-consuming and misleading. 依靠天然的流行既浪费时间,又会引入歧途。
  • The antibiotic epidemics usually start stop when the summer rainy season begins. 传染病通常会在夏天的雨季停止传播。
14 herd Pd8zb     
  • She drove the herd of cattle through the wilderness.她赶着牛群穿过荒野。
  • He had no opinions of his own but simply follow the herd.他从无主见,只是人云亦云。
15 amplified d305c65f3ed83c07379c830f9ade119d     
放大,扩大( amplify的过去式和过去分词 ); 增强; 详述
  • He amplified on his remarks with drawings and figures. 他用图表详细地解释了他的话。
  • He amplified the whole course of the incident. 他详述了事件的全过程。
16 mimic PD2xc     
  • A parrot can mimic a person's voice.鹦鹉能学人的声音。
  • He used to mimic speech peculiarities of another.他过去总是模仿别人讲话的特点。
17 dealing NvjzWP     
  • This store has an excellent reputation for fair dealing.该商店因买卖公道而享有极高的声誉。
  • His fair dealing earned our confidence.他的诚实的行为获得我们的信任。
18 exacerbates 6cfe9141c1cc92f73da37ad4ef8948ca     
n.使恶化,使加重( exacerbate的名词复数 )v.使恶化,使加重( exacerbate的第三人称单数 )
  • Stripping the land in these ways allows faster surface runoff and exacerbates flooding. 这些做法终将使土地裸露、地表径流加快,从而加重了洪水的威胁。 来自辞典例句
  • This policy exacerbates the gap between rich and poor. 这项政策加剧了贫富差距。 来自互联网
19 altruistic hzuzA6     
  • It is superficial to be altruistic without feeling compassion.无慈悲之心却说利他,是为表面。
  • Altruistic spirit should be cultivated by us vigorously.利他的精神是我们应该努力培养的。
20 dilemmas 619646ac13737b880beb161dfe80967f     
n.左右为难( dilemma的名词复数 );窘境,困境
  • They dealt with their dilemmas by mixing perhaps unintentionally an explosive brew. 他们――也许是无意地――把爆炸性的佐料混合在一起,以此来应付困难处境。 来自辞典例句
  • Ten years later we encountered the same dilemmas in Vietnam. 十年后,我们又在越南遇到了同样进退两难的局面。 来自辞典例句
21 scenarios f7c7eeee199dc0ef47fe322cc223be88     
  • Further, graphite cores may be safer than non-graphite cores under some accident scenarios. 再者,根据一些事故解说,石墨堆芯可比非石墨堆芯更安全一些。 来自英汉非文学 - 环境法 - 环境法
  • Again, scenarios should make it clear which modes are acceptable to users in various contexts. 同样,我们可以运用场景剧本来搞清楚在不同情境下哪些模式可被用户接受。 来自About Face 3交互设计精髓
22 influenza J4NyD     
  • They took steps to prevent the spread of influenza.他们采取措施
  • Influenza is an infectious disease.流感是一种传染病。