群体免疫（又称社区免疫）的概念其实非常简单，有疫苗的帮助，没有抗体的人有了抵抗病毒的能力，社群就相对变得安全了很多。
然而当前新冠病毒有疫苗可用么？答案是没有。所以英国当局的“佛系”策略引发了巨大的争论。
也许未来有一天，历史会证明“群体免疫”策略奏效了，但是，这一策略施行的背后隐藏着巨大的风险。而这些风险的承担者，不仅仅是那些高危人群。
“控制疾病不应和政治相关”，这只是痴人说梦。事实上当疾病成为大流行，左右它的，只能是政治。
诚如《柳叶刀》杂志主编Richard Horton所言，想要得到公众的支持，拿出你们决策依据。
2020年3月15日，英国卫报发表了哈佛大学公共卫生学院William Hanage副教授的文章
I’m an epidemiologist. When I heard about Britain’s ‘herd immunity’ coronavirus plan, I thought it was satire《我是一名流行病学家。当我听说了英国新冠病毒“群体免疫”计划，我觉得这真的很讽刺》
以下为全文的大概译文（非逐句翻译），供参考：
Your house is on fire, and the people whom you have trusted with your care are not trying to put it out. Even though they knew it was coming, and could see what happened to the neighbours as they were overwhelmed with terrifying speed, the UK government has inexplicably chosen to encourage the flames, in the misguided notion that somehow they will be able to control them.
嗯，你房子起火，而你信任的人并不帮着你灭火。明知道火势要起来，英国政府选择让火烧下去，大概意思就是，我们能控制住。
When I first heard about this, I could not believe it. I research and teach the evolution and epidemiology of infectious disease at Harvard’s Chan School of Public Health. My colleagues here in the US, even as they are reeling from the stumbling response of the Donald Trump administration to the crisis, assumed that reports of the UK policy were satire – an example of the wry humour for which the country is famed. But they are all too real.
我TM听到这个消息都傻眼了。我在哈佛大学公共卫生学院搞科研搞教学，领域就是流行病的起源、进化、传播这些。虽然我美国的同事让川普当局的措施已经搞蒙了，但是我们就当英国的策略是一种讽刺吧--他们不是以各种讽刺性的幽默出名么。但这一切都太TM过于真实了。
Let me take the arguments on their merits. The stated aim has been to achieve “herd immunity” in order to manage the outbreak and prevent a catastrophic “second wave” next winter – even if Matt Hancock has tried to put that particular genie back in the bottle this weekend. A large proportion of the population is at lower risk of developing severe disease: roughly speaking anyone up to the age of 40. So the reasoning goes that even though in a perfect world we’d not want anyone to take the risk of infection, generating immunity in younger people is a way of protecting the population as a whole.
让我来评价一下他们的是非曲直。为了控制疫情的爆发并预防明年冬天的“第二波”爆发，英国的策略是通过“群体免疫”实现这个目标。对于40岁以下的人来说，感染疾病并且进一步恶化的风险要相对低一些。总之，保护了年轻人，就是保护了整个群体。
We talk about vaccines generating herd immunity, so why is this different? Because this is not a vaccine. This is an actual pandemic that will make a very large number of people sick, and some of them will die. Even though the mortality rate is likely quite low, a small fraction of a very large number is still a large number. And the mortality rate will climb when the NHS is overwhelmed. This would be expected to happen, even if we make the generous assumption that the government were entirely successful in restricting the virus to the low-risk population, at the peak of the outbreak the numbers requiring critical care would be greater than the number of beds available. This is made worse by the fact that people who are badly ill tend to remain so for a long time, which increases the burden.
我们说疫苗帮助形成群体免疫，但这个病毒没有疫苗啊。这是个大流行病，许多人会患病，其中一些人会死去。尽管最终死亡率可能挺低的，但是基数大的话，那是要死很多人的啊。还有，英国医疗卫生体系超负荷运转的时候，死亡率会上升的。这是有可能发生的，往最好的结局想，低风险人群完全控制住了，然而疾病爆发的高峰期需要许多床位，然而现有的床位远远不够。病情严重的人会持续下去很长时间，负担则进一步加大。
And of course you can’t restrict it to this age group. Think of all the people aged between 20 and 40 who work in healthcare, or old people’s homes. You don’t need many introductions into settings like these for what we might coyly call “severe outcomes”. In Washington State, nearly all the deaths reported so far have been associated with nursing homes. Is everyone in a high-risk group supposed to withdraw themselves from society for six months until they can emerge once the (so far entirely imaginary) second wave has been averted?
并且我们也不能就说40岁以下人群风险就低。那些20到40岁之间的照护老年人的年轻人呢？拿华盛顿特区来说，现在死亡案例基本和养老院有关。等第二波被控制住，高风险的人群需要将自己与社会隔离6个月？
About that second wave: let me be clear. Second waves are real things, and we have seen them in flu pandemics. This is not a flu pandemic. Flu rules do not apply. There might well be a second wave, I honestly don’t know. But vulnerable people should not be exposed to a virus right now in the service of a hypothetical future.
关于第二波，我想说清楚。第二波确实有这回事，我们在流感里看到过。可这新冠病毒是流感么？流感的规则不适用新冠。到底有没有第二波，说实话我不知道。但是面对一个未知的未来，脆弱的人群不应现在暴露在病毒之下。
Keeping people safe means self-isolation if you develop symptoms, but the official advice here is also misleading. While it is of paramount importance that sick people stay at home to avoid infecting others, it is increasingly clear that transmission can occur before symptoms develop. We know this is true from modelling and observational studies. I have seen it happen myself. We do not know how often it occurs or how important it is in the epidemiology, but it definitely does happen.
有症状了你就自我隔离，人群就安全了，但是官方的这个建议也有误导性。患病了待在家里避免传染给别人当然非常重要，更重要的是越来越多的证据表明，有症状之前，传染就可以发生。从模型和观察性研究中证实了这是真的。我自己就见证过。在流行病学中，这种现象发生的频率如何，重要性如何还不知道，但是它确实在发生着。
However, arguments about the case fatality rate, the transmission parameters and presymptomatic transmission all miss the point. This virus is capable of shutting down countries. You should not want to be the next after Wuhan, Iran, Italy or Spain. In those places, the healthcare systems have broken down. In Italy, the choices of whom to save and whom to allow to die are real. You should instead look to the example of South Korea, which, through a combination of intense surveillance and social distancing, appears to have gained some semblance of control over the virus. We can learn from South Korea, Singapore, Hong Kong and Taiwan, all of which have so far done a good job mitigating the worst outcomes despite having reported cases early in the pandemic, and in the case of South Korea, suffering a substantial outbreak.
关于致死率，传染性，症状发生之前等方面的争论都忽视了这一点。这个病毒强大到足以封国。你们肯定不希望成为下一个武汉，伊朗，意大利或西班牙。这些地方，医疗系统都崩溃了。在意大利，让谁先死，这事儿是真的。我们应该看看韩国，一系列的措施后，似乎基本上控制了疫情。我们可以好好和韩国，新加坡，香港，台湾学一学，他们都是在初期采取了有效措施避免了悲剧的结果。尤其是韩国，实打实地遭遇了相当的疾病爆发。
The UK should not be trying to create herd immunity, that will take care of itself. Policy should be directed at slowing the outbreak to a (more) manageable rate. What this looks like is strong social distancing. Anyone who can work from home, should. People who do not yet work from home should be encouraged to do so. Employers should guarantee sick pay, including for contacts of known cases, and do everything they can to discourage the practice of “presenteeism”. You should not shake hands. Not with anyone. You should wash your hands for 20 seconds several times a day and whenever you enter your home (or someone else’s home). Call a halt to large gatherings. Educate people about masks and how they should be reserved for the medical professionals who need them. All this and more should have started weeks ago.
英国不应当试图寻求群体免疫保护自己。政策的施行应当是将疾病的爆发控制在一定的比例内。怎么做？别社交了。能在家办公就在家，不能的也应努力做到。雇主们应保证职工患病期间的支出，尽全力避免员工的超时工作。别握手，和谁都不行。每次进家门，洗手，至少20秒。聚会的都省省吧。告诉人们如何用口罩，以及应如何节约口罩以让医疗人员保证有口罩使用。这些措施及其他更多措施几周前就该采取了。
Deciding whether to close schools is hard; they do so much more than just education. But this is a pandemic, and so you should expect they will be shut sooner or later. In Hong Kong, they have been shut for weeks. If you hear any talking head on TV explain that kids don’t get sick, remember that doesn’t mean kids cannot be infected and transmit. It’s probably a good idea to hold off on visits to Nana and Grandpa.
学校到底要不要停课确实是个很难的决定，这比教育本身要重要的多。但是记住了，这是大流行，所以看吧，早晚估计是要停学的。香港都停了好几周了。如果你在电视上听说小朋友不会得病的，记住咯，这并不是说小朋友就一定不会感染这个疾病。最好啊，爷爷奶奶什么的，也别接触了。
The most fundamental function of a government is to keep its people safe. It is from this that it derives its authority, the confidence of the people and its legitimacy. Nobody should be under the illusion that this is something that can be dodged through somehow manipulating a virus that we are only beginning to understand. This will not pass you by; this is not a tornado, it is a hurricane.
政府最最基础的职能是保卫人民的安全。如此你才有人民的授权啊，你的合法性来源于人民。 面对一种全新的病毒，我们知之甚少的病毒，制造出“这不是什么大事儿”的假象，是不对的。 这事谁也做不到事不关己高高挂起。它不是龙卷风，是飓风！
Don’t panic, but do prepare. If your government won’t help you, do it yourself.
别慌但做好准备。政府不助，自助。