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Article History

Received: 22 March 2021

Accepted: 6 October 2021

First Online: 17 October 2021

Declarations

:

: All methods were carried out in accordance with relevant guidelines and regulations. Full ethical approval for this survey was obtained from the Peking University Institutional Review Board on April 26, 2017 (IRB0 0 0 01052–17033). The Board approved the verbal consent procedure and verbal consent was obtained from local health departments. Informed consent was obtained from all participants or, if participants are under 18, from a parent and/or legal guardian. We collected verbal consents for three main reasons: the research presented minimal risk of harm to subjects, involved no procedures for which written consent was normally required outside of the research context, and verbal consents were more culturally acceptable than written consents in the region.

: Not applicable.

: DET and HS are employed by and received a salary respectively from UCB (Belgium) and the Business Development Center (BDC) of the Red Cross Society of China (RCSC). This does not alter our adherence to <i>BMC Public Health</i> policies on sharing data and materials. There are no patents, products in development or marketed products to declare.