Texas Is Setting Itself Up For a Major Measles Epidemic, New Study Warns

一项新的研究警告，德克萨斯州或将面临一场大规模的麻疹疫情

The vaccination rate among school children in Texas is slipping to dangerous levels, and public health experts are now warning of a major measles epidemic.

德克萨斯州学龄儿童的疫苗接种率正在下降到危险的水平，公共卫生专家现在警告说有一场大规模的麻疹流行。

If they're right, it could be one of the largest outbreaks since measles was first declared eliminated in the United States.

如果他们是对的，这可能是自美国首次宣布消除麻疹以来最大的疫情之一。

"At current vaccination rates, there's a significant chance of an outbreak involving more than 400 people right now in some Texas cities," says David Sinclair an expert in health policy and management at the University of Pittsburgh.

匹兹堡大学的健康政策和管理专家大卫·辛克莱说：“按照目前的疫苗接种率，目前在德克萨斯州的一些城市，有很大的可能爆发一场涉及400多人的疫情。”

"We forecast that a continuous reduction in vaccination rates would exponentially increase possible outbreak sizes."

“我们预测，疫苗接种率的持续下降将成倍增加可能的爆发规模。”

These predictions are based on real-world vaccination data, which was plugged into an "agent-based" simulation that runs for the typical length of a school year. This computer model essentially creates a synthetic population that moves around a community in a realistic fashion, from home to work or to school.

这些预测是基于真实的疫苗接种数据，这些数据被插入到一个“基于代理”的模拟中，该模拟运行一个学年的典型长度。这个计算机模型基本上创建了一个综合群体，以一种现实的方式，从家庭到工作或学校，在一个社区中移动。

Using this tool, the team could predict how a measles contagion might spread from individual to individual within and beyond Texas private and public schools. In fact, this same method was used in California in 2015 to help pass a bill restricting vaccine exemptions for school-age children.

利用这个工具，研究小组可以预测麻疹传染病如何在德克萨斯州私立和公立学校内外从个人传播到个人。事实上，加州在2015年也采用了同样的方法来帮助通过一项限制学龄儿童接种疫苗的法案。

Texas is currently the second largest state by population, and its vaccine exemption laws are some of the least effective in the US. Over the years, as more and more parents choose not to vaccinate for personal or religious reasons, Texan cities both large and small have become increasingly vulnerable to the measles virus.

德克萨斯州目前是人口第二大的州，其疫苗豁免法在美国是最不有效的。多年来，由于越来越多的父母出于个人或宗教原因选择不接种疫苗，德克萨斯州的大城市和小城市越来越容易感染麻疹病毒。

Experts are worried that if the trend continues and exemptions are not reduced, the risk of a measles outbreak could become exponentially worse.

专家们担心，如果这种趋势继续下去，不减少豁免的话，麻疹爆发的风险可能会呈指数级恶化。

Since 2003, the number of reported exemptions among Texas students has increased by 28-fold, going from just 2,300 to 64,000 in 2018.

自2003年以来，德克萨斯州学生申请豁免疫苗的人数增加了28倍，从2018年的2300人增加到64000人。

If vaccination rates drop by a further 5 percent, the new research suggests it would increase the size of a potential measles outbreak in some communities by up to 4,000 percent, and could infect nearly a thousand people.

如果疫苗接种率再下降5%，这项新的研究表明，它将使一些社区潜在麻疹爆发的规模增加多达4000%，并可能感染近千人。

"Efforts to achieve or maintain herd immunity have been hampered by a small segment of the population declining vaccinations for their children for various reasons, including concerns regarding adverse effects of vaccination, lack of knowledge of the vaccine, and social influences," the authors explain.

“由于各种原因，包括对疫苗接种的不良影响、对疫苗缺乏了解以及社会影响的担忧，一小部分人口减少了为其子女接种疫苗的数量，这阻碍了实现或维持群体免疫的努力，”作者写道。

Running 1,000 simulations for the current Texas vaccination rate and a 5 percent hypothetical decrease, researchers have now shown that a small number of under-vaccinated bubbles can spark a much wider epidemic.

研究人员对目前德克萨斯州的疫苗接种率进行了1000次模拟，并假设疫苗接种率下降了5%，现在研究人员表明，少量疫苗接种不足的泡沫会引发更广泛的流行病。

Randomly selecting a student whose parents refused to vaccinated, a single case of measles was introduced into the simulation. This one case was then allowed to spread among others in the community who are vulnerable to the virus.

随机选择一名父母拒绝接种疫苗的学生，将一例麻疹引入模拟。这一病例随后被允许在社区中易受病毒感染的人群中传播。

In Austin and Dallas-Fort Worth alone, where many schools are teetering on a dangerously low vaccination rate, the worst simulations ended up with hundreds of measles cases.

仅在奥斯汀和达拉斯沃思堡(Dallas Fort Worth)，许多学校在疫苗接种率极低的情况下摇摇欲坠，最糟糕的模拟结果就有数百起麻疹病例。

In Dallas-Fort Worth, the authors say there are 13 schools with vaccination rates less than 92 percent, which is the lower end of the herd immunity threshold. In Austin, there are 35 schools who have dropped below this crucial level.

在达拉斯-沃思堡，作者说有13所学校的疫苗接种率低于92%，这是群体免疫阈值的下限。在奥斯汀，有35所学校低于这一关键水平。

"The simulations suggest that large outbreaks occur where there is a significant population of students for whom a vaccine has been refused; however, infections are not limited to those students," the authors write.

作者写道：“模拟表明，在有大量学生拒绝接种疫苗的情况下，会发生大规模疫情;然而，感染并不局限于这些学生。”

In all the scenarios where more than 25 people became infected, 64 percent of those cases occurred in students whose parents had refused to vaccine them, while 36 percent occurred in innocent bystanders, who either can't be vaccinated or whose vaccinations did not provide full immunity.

在所有超过25人感染的情况下，64%的病例发生在拒绝接种疫苗的学生身上，36%发生在无辜的旁观者身上，他们要么不能接种疫苗，要么接种的疫苗不能提供完全免疫。

When the vaccination rate was decreased by a further 5 percent, the cases skyrocketed. Across the entire state, outbreaks bloomed in every metropolitan area, including Houston, infecting between 500 and a thousand people in just one year.

当疫苗接种率再降低5%时，病例就会激增。在全州范围内，疫情在包括休斯顿在内的每一个大城市爆发，仅在一年内就感染了500至1000人。

An outbreak of half a thousand people or more would be unprecedented in the state of Texas and would disproportionately affect children. In 2009 to 2017 in Texas, 60 percent of measles cases occurred in kids younger than 19 years, and the largest of these involved only 25 cases.

在德克萨斯州，5000人或更多的人爆发疫情将是前所未有的，而且会不成比例地影响到儿童。2009年至2017年，德克萨斯州60%的麻疹病例发生在19岁以下的儿童中，其中最大的范围仅涉及25例。

William Moss, an epidemiologist at Johns Hopkins who was not involved in the study told Newsweek he was surprised by these extreme results.

约翰霍普金斯大学的流行病学家威廉·莫斯没有参与这项研究，他告诉《新闻周刊》，他对这些极端的结果感到惊讶。

"We tend to think in terms of linear relationships, and thus that a 5 percent decrease in vaccination coverage might result in a 5 percent increase in potential outbreak size, but in fact the relationship is exponential," Moss explains.

莫斯解释说：“我们倾向于从线性关系的角度来考虑，认为疫苗接种覆盖率下降5%，可能导致潜在爆发规模增加5%，但实际上，这种关系是指数级的。”

"This is very important from a public health perspective: small decreases in measles vaccination coverage can have large consequences."

“从公共卫生的角度来看，这一点非常重要：麻疹疫苗接种覆盖率的小幅下降，可能会产生巨大的后果。”