Acknowledgements
We thank the study participants and the staff that collected the blood samples at the Clinical and Research Center of Infectious Disease, Beijing Ditan Hospital. This work was funded by National Science and Technology Major Project during the ’13th Five-year’ Plan Period (No.2017ZX10205502).
Author contributions
Li Li, Cheng-jie Ma and Xing-wang Li conceived the study and designed the protocol. Li Li, Feng-ting Yu and Shu-jing Song performed the experiments. Li Li, Ling-hang Wang and Si-yuan Yang analyzed obtained data. Li Li and Yun-xia Tang collected samples. Cheng-jie Ma and Xing-wang Li supervised the project. Li Li wrote the manuscript. All authors have reviewed the final version of the manuscript and approved its submission for publishing.