He, Haizhen
Zhang, Ting
Zhou, Jing
Zhu, Zhu
Na, Xiaona
Zhou, Guirong
Zhuang, Guoliang
Liu, Aiping
Funding for this research was provided by:
Health and Family Planning Commission and Disease Control and Prevention Center of Mentougou of Beijing, China
Article History
Received: 25 November 2018
Accepted: 30 April 2019
First Online: 22 May 2019
Competing Interests
: The authors declare no competing interests.