Immune Protection Induced on Day 10 Following Administration of the 2009 A/H1N1 Pandemic Influenza Vaccine

Abstract

BackgroundThe 2009 swine-origin influenza virus (S-OIV) H1N1 pandemic has caused more than 18,000 deaths worldwide. Vaccines against the 2009 A/H1N1 influenza virus are useful for preventing infection and controlling the pandemic. The kinetics of the immune response following vaccination with the 2009 A/H1N1 influenza vaccine need further investigation.Methodology/Principal Findings58 volunteers were vaccinated with a 2009 A/H1N1 pandemic influenza monovalent split-virus vaccine (15 µg, single-dose). The sera were collected before Day 0 (pre-vaccination) and on Days 3, 5, 10, 14, 21, 30, 45 and 60 post vaccination. Specific antibody responses induced by the vaccination were analyzed using hemagglutination inhibition (HI) assay and enzyme-linked immunosorbent assay (ELISA). After administration of the 2009 A/H1N1 influenza vaccine, specific and protective antibody response with a major subtype of IgG was sufficiently developed as early as Day 10 (seroprotection rate: 93%). This specific antibody response could maintain for at least 60 days without significant reduction. Antibody response induced by the 2009 A/H1N1 influenza vaccine could not render protection against seasonal H1N1 influenza (seroconversion rate: 3% on Day 21). However, volunteers with higher pre-existing seasonal influenza antibody levels (pre-vaccination HI titer ≥1∶40, Group 1) more easily developed a strong antibody protection effect against the 2009 A/H1N1 influenza vaccine as compared with those showing lower pre-existing seasonal influenza antibody levels (pre-vaccination HI titer <1∶40, Group 2). The titer of the specific antibody against the 2009 A/H1N1 influenza was much higher in Group 1 (geometric mean titer: 146 on Day 21) than that in Group 2 (geometric mean titer: 70 on Day 21).Conclusions/SignificanceRecipients could gain sufficient protection as early as 10 days after vaccine administration. The protection could last at least 60 days. Individuals with a stronger pre-existing seasonal influenza antibody response may have a relatively higher potential for developing a stronger humoral immune response after vaccination with the 2009 A/H1N1 pandemic influenza vaccine.

Meta-Analysis of the Immunogenicity and Tolerability of Pandemic Influenza A 2009 (H1N1) Vaccines

“…Fourteen studies were single-arm (with respect to pandemic vaccines) or non-randomized trials and were thus included in proportion meta-analyses only [9], [13], [14], [16], [21], [22], [27], [31], [32], [34], [55], [57], [58]. One of the above papers also reported data on a randomized clinical trial (RCT) [55], as did the remaining 19 papers, which reported the results of another 21 RCTs [8], [11], [12], [15], [17], [18], [19], [23], [24], [25], [26], [28], [29], [30], [33], [35], [37], [39], [54], [59], for a total of 22 RCTs.…”

High Titer and Avidity of Nonneutralizing Antibodies against Influenza Vaccine Antigen Are Associated with Severe Influenza

“…One of the key functions of an- or more are associated with protection from influenza virus infection and are often used as markers of successful immunization in influenza vaccine trials (23,30). During the first few days of an infection, the neutralizing antibody titers are often low (34). However, the magnitude of nonneutralizing antibodies during this period has not been studied.…”

Serum immunoglobulin G subclass levels and estimated clinical severity caused by possible influenza A (H1N1) pdm 2009 infection

“…Moreover, a recent report [24] revealed that a neutralizing antibody to protect against H1N1 pdm09 infection increased as early as 10 days after vaccination against H1N1 pdm09. In addition, a stronger response to increase the neutralizing antibody to H1N1 pdm09 was observed in individuals with an elevated preexisting seasonal influenza antibody.…”