Challenges Remain for Influenza Vaccination of Children

Journal of Infectious Diseases
Volume 214 Issue 10 November 15, 2016

Challenges Remain for Influenza Vaccination of Children
J Infect Dis. (2016) 214 (10): 1470-1472 doi:10.1093/infdis/jiw384
Kathryn M. Edwards and Wendy A. Keitel
Over the past decades, multiple active surveillance and observational studies have demonstrated the major impact of influenza on children and underscored the need for effective vaccines [1–4]. Since 2009, annual influenza vaccination has been recommended for all children ≥6 months of age in the United States [5]. Extensive studies in children have been conducted over the years with both inactivated influenza vaccines (IIV) and live attenuated influenza vaccines (LAIV). Influenza hemagglutination inhibition (HAI) antibody responses are considered to be the gold standard for assessing IIV immunogenicity and serve as the basis for their licensure. Although achievement of HAI antibody titers of ≥40 (putative protective titer) was associated with a 50% reduction in the occurrence of influenza [6, 7], others have proposed that the protective HAI titer is much higher [8]. Furthermore, there can be variability in HAI assay results among laboratories [9]. Cell-mediated immune (CMI) responses have been less well characterized, and no CMI correlate of protection (COP) has been proposed.’

In this issue of The Journal of Infectious Diseases, Reber et al report detailed humoral and CMI responses in 50 children ages 9–14 years after receipt of the 2010–2011 seasonal IIV [10]. In the previous year, 38% of the participants had received influenza vaccine (10% received LAIV and 28% received IIV), and 32% had been immunized with monovalent 2009 pandemic influenza A(H1N1) vaccine. Which vaccine(s) the children had received previously was not noted in the article, and their impact on subsequent immune responses was not assessed because of small sample size. HAI antibody responses were assayed against influenza virus antigens included in both the 2009–2010 and 2010–2011 vaccines, as well as the …