德克薩斯州或?qū)⒚媾R一場大規(guī)模的麻疹疫情

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

一項新的研究警告，德克薩斯州或?qū)⒚媾R一場大規(guī)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.

德克薩斯州學齡兒童的疫苗接種率正在下降到危險的水平，公共衛(wèi)生專家現(xiàn)在警告說有一場大規(guī)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.

如果他們是對的，這可能是自美國首次宣布消除麻疹以來最大的疫情之一。

"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.

匹茲堡大學的健康政策和管理專家大衛(wèi)·辛克萊說：“按照目前的疫苗接種率，目前在德克薩斯州的一些城市，有很大的可能爆發(fā)一場涉及400多人的疫情。”

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

“我們預測，疫苗接種率的持續(xù)下降將成倍增加可能的爆發(fā)規(guī)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.

這些預測是基于真實的疫苗接種數(shù)據(jù)，這些數(shù)據(jù)被插入到一個“基于代理”的模擬中，該模擬運行一個學年的典型長度。這個計算機模型基本上創(chuàng)建了一個綜合群體，以一種現(xiàn)實的方式，從家庭到工作或?qū)W校，在一個社區(qū)中移動。

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.

利用這個工具，研究小組可以預測麻疹傳染病如何在德克薩斯州私立和公立學校內(nèi)外從個人傳播到個人。事實上，加州在2015年也采用了同樣的方法來幫助通過一項限制學齡兒童接種疫苗的法案。

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.

德克薩斯州目前是人口第二大的州，其疫苗豁免法在美國是最不有效的。多年來，由于越來越多的父母出于個人或宗教原因選擇不接種疫苗，德克薩斯州的大城市和小城市越來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.

專家們擔心，如果這種趨勢繼續(xù)下去，不減少豁免的話，麻疹爆發(fā)的風險可能會呈指數(shù)級惡化。

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年以來，德克薩斯州學生申請豁免疫苗的人數(shù)增加了28倍，從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.

如果疫苗接種率再下降5%，這項新的研究表明，它將使一些社區(qū)潛在麻疹爆發(fā)的規(guī)模增加多達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.

“由于各種原因，包括對疫苗接種的不良影響、對疫苗缺乏了解以及社會影響的擔憂，一小部分人口減少了為其子女接種疫苗的數(shù)量，這阻礙了實現(xiàn)或維持群體免疫的努力，”作者寫道。

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.

研究人員對目前德克薩斯州的疫苗接種率進行了1000次模擬，并假設疫苗接種率下降了5%，現(xiàn)在研究人員表明，少量疫苗接種不足的泡沫會引發(fā)更廣泛的流行病。

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.

隨機選擇一名父母拒絕接種疫苗的學生，將一例麻疹引入模擬。這一病例隨后被允許在社區(qū)中易受病毒感染的人群中傳播。

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.

僅在奧斯汀和達拉斯沃思堡(Dallas Fort Worth)，許多學校在疫苗接種率極低的情況下?lián)u搖欲墜，最糟糕的模擬結(jié)果就有數(shù)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.

在達拉斯-沃思堡，作者說有13所學校的疫苗接種率低于92%，這是群體免疫閾值的下限。在奧斯汀，有35所學校低于這一關(guān)鍵水平。

"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.

作者寫道：“模擬表明，在有大量學生拒絕接種疫苗的情況下，會發(fā)生大規(guī)模疫情;然而，感染并不局限于這些學生。”

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.

在所有超過25人感染的情況下，64%的病例發(fā)生在拒絕接種疫苗的學生身上，36%發(fā)生在無辜的旁觀者身上，他們要么不能接種疫苗，要么接種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.

當疫苗接種率再降低5%時，病例就會激增。在全州范圍內(nèi)，疫情在包括休斯頓在內(nèi)的每一個大城市爆發(fā)，僅在一年內(nèi)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.

在德克薩斯州，5000人或更多的人爆發(fā)疫情將是前所未有的，而且會不成比例地影響到兒童。2009年至2017年，德克薩斯州60%的麻疹病例發(fā)生在19歲以下的兒童中，其中最大的范圍僅涉及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.

約翰霍普金斯大學的流行病學家威廉·莫斯沒有參與這項研究，他告訴《新聞周刊》，他對這些極端的結(jié)果感到驚訝。

"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.

莫斯解釋說：“我們傾向于從線性關(guān)系的角度來考慮，認為疫苗接種覆蓋率下降5%，可能導致潛在爆發(fā)規(guī)模增加5%，但實際上，這種關(guān)系是指數(shù)級的。”

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

“從公共衛(wèi)生的角度來看，這一點非常重要：麻疹疫苗接種覆蓋率的小幅下降，可能會產(chǎn)生巨大的后果。”