In the 535 samples taken in March (229 male and 306 female), the log2 GMTs for A/H1N1, A/H3N2, B/Y and B/V were 3.5721.313, 3.7781.235, 4.2791.591 and 3.9051.725, respectively (Table 1). and age distribution of samples in March 2009 for serum antibodies against influenza B/Victoria by HI. (DOCX) pone.0053847.s006.docx (14K) GUID:?5ECB4BB7-975C-4BC4-8C7E-6D6D2993457C Table S7: Titre and age distribution of samples in September 2009 for serum antibodies against seasonal H1N1 by HI. (DOCX) pone.0053847.s007.docx (14K) GUID:?469AB9D7-47C3-45A2-9CAD-C7D23904D291 Table S8: Titre and age distribution of samples in September 2009 for serum antibodies against seasonal H3N2 by HI. (DOCX) pone.0053847.s008.docx (14K) GUID:?09D4E1C5-BEC9-4B12-8217-1AD137A9C754 Table S9: Titre and age distribution of samples in September 2009 for serum antibodies against influenza B/Yamagata by HI. (DOCX) pone.0053847.s009.docx (14K) GUID:?5E81239E-164F-4613-B0C8-0D43634A8A01 Table S10: Titre and age distribution of samples in September 2009 for serum antibodies against influenza B/Victoria by HI. (DOCX) BMS-986158 pone.0053847.s010.docx (14K) GUID:?20973AFC-D172-4913-ABDD-B219C6CB2A82 Table S11: 2009 March H1N1 HI titer distribution. (DOCX) pone.0053847.s011.docx (13K) GUID:?C75A527B-98BB-45D7-A50B-B2FBD4789E62 Table S12: 2009 March H3N2 HI titer distribution. (DOCX) pone.0053847.s012.docx (13K) GUID:?D8AFA780-D42B-4C60-A23A-773EE6A901A0 Table S13: 2009 March B/Y HI titer distribution. (DOCX) pone.0053847.s013.docx (13K) GUID:?F9C292B9-ED8F-48BF-AE92-E5A7C0FF8F00 Table S14: 2009 March B/V HI titer distribution. (DOCX) pone.0053847.s014.docx (13K) GUID:?CBC3FDCC-FA0B-4671-88CC-9686780C66FB Table S15: 2009 September H1N1 HI titer distribution. (DOCX) pone.0053847.s015.docx (13K) GUID:?B4CE99C1-875F-4417-91D1-447103318F84 Table S16: 2009 September H3N2 HI titer distribution. (DOCX) pone.0053847.s016.docx (13K) GUID:?F4D4D351-6BA5-4FED-B0CD-D07181449F17 Table S17: 2009 September B/Y HI titer distribution. (DOCX) pone.0053847.s017.docx (13K) GUID:?11FAD1A5-9514-4DDB-B4AA-FACC2231726D Table S18: 2009 September B/V HI Tal1 titer distribution. (DOCX) pone.0053847.s018.docx (14K) GUID:?B7D3D10F-85F7-4DC2-AC4D-009A98F38E80 Abstract Much information is available for the 2009 2009 H1N1 influenza immunity response, but little is known about the antibody switch in seasonal influenza before and during the novel influenza A pandemic. In this study, we conducted a cross-sectional serological survey of 4 types of major seasonal influenza in March and September 2009 on a full range of age groups, to investigate seasonal influenza immunity response before and during the outbreak of the sH1N1 influenza in Shenzhen C the largest migration city in China. We found that the 0C5 age group had an increased antibody level for all types of seasonal influenza during the pandemic compared to the pre-outbreak level, in contrast with almost all other age groups, in which the antibody level decreased. Also, distinct from your antibodies of A/H3N2, B/Yamagata and B/Victoria that decreased significantly during the 2009 H1N1 pandemic, the antibody of A/H1N1 showed no statistical difference from your pre-outbreak level. The results suggest that the antibodies against the 2009 2009 sH1N1 cross-reacted with seasonal H1N1. Moreover, the 0C5 age group was under attack by both seasonal and 2009 H1N1 influenza during the pandemic, hence vaccination merely against a new strain of flu might not be enough to protect the youngest group. Introduction In 2009 2009, a swine-origin H1N1 computer virus spread rapidly around the world. The initial outbreak occurred in April of that 12 months in Mexico, and the World Health Business (WHO) declared a global pandemic of the new type of influenza A in June 2009 [1]. By November 2009, 199 countries or regions experienced recognized the computer virus in laboratory. Although the 2009 2009 H1N1 computer virus (also referred as to swine flu, sH1N1) is usually antigenically different from previous seasonal influenza A (H1N1) [2], [3], you will find increasing BMS-986158 reports showing possible cross-reactivity of the antibodies to seasonal influenza antigens [4], [5], [6]. The natural immune response to the 2009 2009 H1N1 has been extensively investigated [7], [8], and the status of the antibody against sH1N1 in risk populations before and after the pandemic has been repeatedly reported [9], [10]. However, few reports show the changes in seasonal influenza antibodies before and during the pandemic in risk populations, especially in Asia. In this study we conducted a cross-sectional serological survey of four major seasonal influenza types: A/H1N1, A/H3N2, B/Yamagata (B/Y) and B/Victoria (B/V) in March and September 2009, to investigate the seasonal influenza immunity response before and during the outbreak of the sH1N1 influenza. BMS-986158 Cross-reactivity between antibodies of 2009 H1N1 and seasonal H1N1 is usually speculated..