Original antigenic sin may exist in the influenza virus infection or vaccination, which possibly reduces the protective efficacy in repeated influenza vaccination. This paper reviews the literature on the original antigenic sin and its influence in influenza vaccination, and interprets the possible mechanism of this phenomenon from the three aspects of influenza virus structure, humoral immunity and cellular immunity. A large number of studies have shown that original antigen sin has a negative impact on influenza vaccination, but the evidence disproveing this phenomenon also exist, so multi?center large?scale clinical trials should be conducted to provide evidence?based basis for reaearching whether original antigen sin exists and its effects. in order to provide reference for the development and update of noval influenza vaccines and its formulation of immunization strategies.

Original antigenic sin may exist in the influenza virus infection or vaccination, which possibly reduces the protective efficacy in repeated influenza vaccination. This paper reviews the literature on the original antigenic sin and its influence in influenza vaccination, and interprets the possible mechanism of this phenomenon from the three aspects of influenza virus structure, humoral immunity and cellular immunity. A large number of studies have shown that original antigen sin has a negative impact on influenza vaccination, but the evidence disproveing this phenomenon also exist, so multi?center large?scale clinical trials should be conducted to provide evidence?based basis for reaearching whether original antigen sin exists and its effects. in order to provide reference for the development and update of noval influenza vaccines and its formulation of immunization strategies.

Original antigenic sin may exist in the influenza virus infection or vaccination, which possibly reduces the protective efficacy in repeated influenza vaccination. This paper reviews the literature on the original antigenic sin and its influence in influenza vaccination, and interprets the possible mechanism of this phenomenon from the three aspects of influenza virus structure, humoral immunity and cellular immunity. A large number of studies have shown that original antigen sin has a negative impact on influenza vaccination, but the evidence disproveing this phenomenon also exist, so multi-center large-scale clinical trials should be conducted to provide evidence-based basis for reaearching whether original antigen sin exists and its effects. in order to provide reference for the development and update of noval influenza vaccines and its formulation of immunization strategies.

Objective:To evaluate and share the novel method for recruiting participants in clinical trials of vaccines in emergency situations.Methods:To publish recruitment notice in local areas of Wuhan through websites and medium, and guide interested persons to log in to the“Clinical Trials of SARS-CoV-2 Vaccine Reservation and Health Declaration System”to appoint and register their health information. The "Health Declaration System" provides each volunteer evaluation and risk levels to preliminarily exclude those who do not meet the inclusion criteria. Researchers review the qualified volunteers by telephone, organize them to go to the vaccination site, and finally conduct a strict medical screening to determine the final subjects.Results:A total of 4 819 people and 5 132 people registered in the Phase Ⅰ and Phase Ⅱ recruitment system respectively, with men 2 912 (60.43%) and 2 887 (56.25%) more than women 1 907 (39.57%) and 2 245 (43.75%), mostly in the 20-39 age group, with 3 211 (66.63%) and 3 966 (77.28%). All 13 districts in Wuhan have interested residents to participate clinical research.The initial qualified rate of the Phase Ⅱ recruitment system was higher than that of Phase Ⅰ, with men 2 047 (70.28%) and 2 135(73.95%), higher than women 1 083 (56.80%) and 1 472 (65.57%); 440 and 689 people were reviewed by telephone in Phase Ⅰ and Phase Ⅱ respectively, and the number of verified volunteers was about 440 (35.00%) and 689 (67.20%); Of the 201 603 people who arrived at the vaccination site, 12 and 26 of them were positive for the SARS-CoV-2 antibody with an antibody positive rate of 6.00% and 4.31% respectively.Conclusion:The novel method for recruiting subjects in this clinical study is efficient and reliable, and the recruitment situation of Phase Ⅰ had set a good example for Phase Ⅱ but the medium-and long-term compliance of subjects and the separation of willingness and behaviors still need to be further studied.

Objective:To evaluate and share the novel method for recruiting participants in clinical trials of vaccines in emergency situations.Methods:To publish recruitment notice in local areas of Wuhan through websites and medium, and guide interested persons to log in to the“Clinical Trials of SARS-CoV-2 Vaccine Reservation and Health Declaration System”to appoint and register their health information. The "Health Declaration System" provides each volunteer evaluation and risk levels to preliminarily exclude those who do not meet the inclusion criteria. Researchers review the qualified volunteers by telephone, organize them to go to the vaccination site, and finally conduct a strict medical screening to determine the final subjects.Results:A total of 4 819 people and 5 132 people registered in the Phase Ⅰ and Phase Ⅱ recruitment system respectively, with men 2 912 (60.43%) and 2 887 (56.25%) more than women 1 907 (39.57%) and 2 245 (43.75%), mostly in the 20-39 age group, with 3 211 (66.63%) and 3 966 (77.28%). All 13 districts in Wuhan have interested residents to participate clinical research.The initial qualified rate of the Phase Ⅱ recruitment system was higher than that of Phase Ⅰ, with men 2 047 (70.28%) and 2 135(73.95%), higher than women 1 083 (56.80%) and 1 472 (65.57%); 440 and 689 people were reviewed by telephone in Phase Ⅰ and Phase Ⅱ respectively, and the number of verified volunteers was about 440 (35.00%) and 689 (67.20%); Of the 201 603 people who arrived at the vaccination site, 12 and 26 of them were positive for the SARS-CoV-2 antibody with an antibody positive rate of 6.00% and 4.31% respectively.Conclusion:The novel method for recruiting subjects in this clinical study is efficient and reliable, and the recruitment situation of Phase Ⅰ had set a good example for Phase Ⅱ but the medium-and long-term compliance of subjects and the separation of willingness and behaviors still need to be further studied.