“THEY hang out in pockets,” says Richard Pan, a Sacramento paediatrician and member of California’s legislature. He is referring to parents who, invoking a “philosophical exemption”, opt not to give their children the state-recommended vaccinations. In some pockets, such as the rural foothills of California’s Sierra Nevada, they may belong to the conservative don’t-tread-on-me crowd that distrusts all government recommendations simply because they come from the government. In others, such as the liberal organic-food-and-yoga belt along the coast, parents may forswear vaccines because they see the shots as dangerous, and the diseases they protect against as mild.
“他们常出现在一些比较另类的小地方。”说这话的是理查德-潘，他是萨科拉门托的一名儿科医生，也是加州立法机构的成员。他说的“他们”是那些援引“哲学豁免”规定，不给自己孩子注射州推荐疫苗的父母们。有些地方，比如加州内华达山脉丘陵地区的乡村，那里可能有保守的、以“不要踩我”为信条的民众，他们不相信所有政府推荐的东西，仅仅因为那是政府推荐的。在其他地方，比如沿海的“有机食品和瑜加”地带，这里的人们包容开放，但父母可能也会不给孩子接种疫苗。他们认为注射疫苗很危险，只能预防一些头疼脑热的小病。
These local concentrations of unvaccinated children pose a growing risk to public health. For the most common shots, vaccination rates for America overall, and even California, are still above 90%, at or near the levels considered necessary to provide “herd immunity” for a population. But in places the rates have been falling for almost a decade. In many counties, towns and nursery schools--within Washington state, Oregon, Vermont and California, especially—vaccination rates are now far below the herd-immunity level.
未接种疫苗的孩子集中在一个地区给公共健康造成的风险越来越大。在美国，甚至加州，大多数普通疫苗的总体接种率仍高于90%，达到或接近公认的“群体免疫”所要求的水平。但在有些地方，差不多有10年，接种率一直在下降。现在，许多县、镇以及托儿所（特别是华盛顿、俄勒冈、佛蒙特、加利福尼亚等州），接种率远远低于群体免疫水平。
This trend, predictably, is leading to the resurgence of diseases considered vanquished long ago. In 2010, for example, California had an outbreak of whooping cough, which at its height put 455 babies in hospital and killed ten of them. Elsewhere there have been outbreaks of measles.
可以预见，任由这种情况发展下去，人们认为早被征服了的一些疾病又会卷土重来。比如，2010年，加州百日咳爆发，最严重时，有455个孩子住进医院，10个孩子因此丧生。还有的地区爆发过麻疹。
The case for vaccination is clear. First, it makes the vaccinated individual either immune or resistant to a disease. Second, and more important, it interferes with contagion and thus makes the entire community safer, including those members, like newborn babies or the very sick, who cannot be vaccinated for medical reasons. The vaccination rate for herd immunity varies by disease, but usually falls between 85% and 95%.
支持疫苗接种的理由比较清楚。首先，它使接种个体具有免疫力，增强抗病能力；第二，这一点也更重要，它阻止疾病传播，使整个社区更加安全，其中包括那些回医疗原因不能接种的新生儿和重病者。不同的疾病对群体免疫接种率的要求不同，但通常应在85%到95%之间。
The case against vaccination, by contrast, is not clear. One view seems to be that the diseases in question merely give you a rash and are a nuisance, whereas the vaccines will make your child autistic. That particular myth, still peddled on the internet, originated with Andrew Wakefield, a British doctor, who published a paper in 1998 that suggested a link between the common MMR shot (against measles, mumps and rubella) and autism. The paper has since been entirely discredited, and Dr Wakefield censured.
比较而言，反对疫苗接种的理由就没那么清楚。一种观点似乎是这样的：疫苗所能预防的不过是些皮疹之类的小毛病，而接种会使你的孩子变得孤僻。仍在网上流传的这个荒诞说法源自英国一位名叫安德鲁•韦克菲尔德的医生，1998年他在一篇文章中提出，常见的MMR接种（预防麻疹、腮腺炎和风疹）和孤独症之间存在关联。从那以后，人们就没有相信过这篇文章的说法，韦克菲尔德博士也受到了公开谴责。