Impact of prior infection and repeated vaccination on post-vaccination antibody titers of the influenza A(H1N1)pdm09 strain in Taiwan schoolchildren: Implications for public health

• Published in: Vaccine 2022-05, Vol.40 (24), p.3402-3411
• Main Authors: Liu, Wei, Lien, Yu-Hui, Lee, Ping-Ing, Chan, Ta-Chien, Wang, Lih-Chiann, Yang, Chin-Rur, Ho, Mei-Shang, Chen, Juine-Ruey, Ku, Chia-Chi, King, Chwan-Chuen
• Format: Article
• Language: English
• Subjects: A(H1N1)pdm09 virus; Antibodies; Antibody response; Antigens; Children; Confidence intervals; Data analysis; Elementary schools; Epidemiology; Exposure history; Guardians; Health facilities; Hemagglutination inhibition; Inactivated influenza vaccine; Infections; Influenza; Influenza A; Pandemics; Public health; Repeated vaccination; Schoolchildren; Seasons; Serology; Taiwan; Vaccine efficacy; Vaccines; Viruses
• ISSN: 0264-410X; 1873-2518
• DOI: 10.1016/j.vaccine.2022.03.047

•Prior infection and vaccination enhance post-vaccination influenza antibody responses.•Pre-vaccination antibody levels determine the effect of booster immunization.•Annual TIV vaccination for schoolchildren prevents influenza virus infection. The objective of this study was to evaluate the effects of prior-infection and repeated vaccination on post-vaccination antibody titers. A(H1N1)pdm09 strain was included in 2009 pandemic monovalent, 2010–2011, and 2011–2012 trivalent influenza vaccines (MIVpdm09, TIV10/11, TIV11/12) in Taiwan. During the 2011–2012 influenza season, we conducted a prospective sero-epidemiological cohort study among schoolchildren from grades 1 – 6 in the two elementary schools in Taipei with documented A(H1N1)pdm09 vaccination records since 2009. Serum samples were collected at pre-vaccination, 1-month, and 4-months post-vaccination (T1, T2, T3). Anti-A(H1N1)pdm09 hemagglutination inhibition titers (HI-Ab-titers) were examined. We also investigated the impact of four vaccination histories [(1) no previous vaccination (None), (2) vaccinated in 2009–2010 season (09v), (3) vaccinated in 2010–2011 season (10v), and (4) vaccinated consecutively in 2009–2010 and 2010–2011 seasons (09v + 10v)] and pre-vaccination HI-Ab levels on post-vaccination HI-Ab responses as well as adjusted vaccine effectiveness (aVE) against serologically-defined infection from T2 to T3. TIV11/12 had zero serious adverse events reported. A(H1N1)pdm09 strain in TIV11/12 elicited seroprotective Ab-titers in 98% of children and showed promising protection (aVE: 70.3% [95% confidence interval (CI): 51.0–82.1%]). Previously unvaccinated but infected children had a 3.96 times higher T2 geometric mean titer (T2-GMT) of HI-Ab than those naïve to A(H1N1)pdm09 (GMT [95% CI]: 1039.7[585.3–1845.9] vs. 262.5[65.9–1045], p = 0.046). Previously vaccinated children with seroprotective T1-Ab-titers had a higher T2-GMT and a greater aVE than those with non-seroprotective T1-Ab-titers. Repeatedly vaccinated children had lower T2-GMT than those receiving primary doses of TIV11/12. However, after controlling prior infection and T1-Ab-titers, differences in T2-GMT among the four vaccination histories became insignificant (p = 0.16). This study supports the implementation of annual mass-vaccination with A(H1N1)pdm09 in schoolchildren for three consecutive influenza seasons when vaccine and circulating strains were well matched, and found that prior infection and pre-vaccination HI-Ab level