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CHINA - SEPTEMBER 17: School children roll up their sleeves to receive injections of the Hepatitis B vaccine in Ledu, Qinghai, China, on Monday, Sept. 17, 2007. Run by the Asian Liver Center at Stanford University, this Hepatitis B vaccination drive is the largest vaccination campaign ever organized in China with 500, 000 children to be vaccinated. (Photo by Aaron Deemer/Bloomberg via Getty Images)

CHINA - SEPTEMBER 17:  School children roll up their sleeves to receive injections of the Hepatitis B vaccine in Ledu, Qinghai, China, on Monday, Sept. 17, 2007. Run by the Asian Liver Center at Stanford University, this Hepatitis B vaccination drive is the largest vaccination campaign ever organized in China with 500, 000 children to be vaccinated.  (Photo by Aaron Deemer/Bloomberg via Getty Images)

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A student receives a H1N1 vaccine injection at a hospital in Suining, Sichuan province November 11, 2009. VCP (Photo by Jie Zhao/Corbis via Getty Images)

A student receives a H1N1 vaccine injection at a hospital in Suining, Sichuan province November 11, 2009. VCP (Photo by Jie Zhao/Corbis via Getty Images)

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RONG AN, CHINA - JULY 23: A nurse checks a baby after vaccination shot at a hospital on July 23, 2018 in Rong an County, Guangxi Zhuang Autonomous Region of China. President Xi Jinping has demanded a thorough investigation into the country's illegal vaccine scandal and serious punishment of those responsible, is has been reported. (Photo by VCG via Getty Images)

RONG AN, CHINA - JULY 23: A nurse checks a baby after vaccination shot at a hospital on July 23, 2018 in Rong an County, Guangxi Zhuang Autonomous Region of China. President Xi Jinping has demanded a thorough investigation into the country's illegal vaccine scandal and serious punishment of those responsible, is has been reported. (Photo by VCG via Getty Images)

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RONG AN, CHINA - JULY 23: Officers of local market regulation administration inspect DPT (Diphtheria, Pertussis, Tetanus) vaccinations produced by Wuhan Institute of Biological Products Co.,Ltd. at the Center for Disease Control and Prevention (CDC) on July 23, 2018 in Rong an County, Guangxi Zhuang Autonomous Region of China. President Xi Jinping has demanded a thorough investigation into the country's illegal vaccine scandal and serious punishment of those responsible, it has been reported. (Photo by VCG via Getty Images)

RONG AN, CHINA - JULY 23: Officers of local market regulation administration inspect DPT (Diphtheria, Pertussis, Tetanus) vaccinations produced by Wuhan Institute of Biological Products Co.,Ltd. at the Center for Disease Control and Prevention (CDC) on July 23, 2018 in Rong an County, Guangxi Zhuang Autonomous Region of China. President Xi Jinping has demanded a thorough investigation into the country's illegal vaccine scandal and serious punishment of those responsible, it has been reported. (Photo by VCG via Getty Images)

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HUANGSHAN, CHINA - JULY 23: View of sealed boxes of freeze-dried rabies vaccines for human use produced by Changchun Changsheng Bio-tech Co at the Center for Disease Control and Prevention (CDC) on July 23, 2018 in Huangshan, Anhui Province of China. President Xi Jinping has demanded a thorough investigation into the country's illegal vaccine scandal and serious punishment of those responsible, it has been reported. (Photo by VCG via Getty Images)

HUANGSHAN, CHINA - JULY 23: View of sealed boxes of freeze-dried rabies vaccines for human use produced by Changchun Changsheng Bio-tech Co at the Center for Disease Control and Prevention (CDC) on July 23, 2018 in Huangshan, Anhui Province of China. President Xi Jinping has demanded a thorough investigation into the country's illegal vaccine scandal and serious punishment of those responsible, it has been reported. (Photo by VCG via Getty Images)