A double-dose inactivated quadrivalent influenza vaccine (IIV4) could be administered to all children aged 6-35 months, as it not only offers the best protection against influenza type B, but it also allows for simplifying the current vaccination schedule considerably.
“The introduction of IIV4 provides an opportunity to review long-accepted practices in administration of influenza vaccines,” explained Varsha K. Jain, MD, formerly employed by GlaxoSmithKline Vaccines, King of Prussia, Pa., and associates.
Cynthia Goldsmith/CDC photo #10073
This negative-stained transmission electron micrograph (TEM) depicts the ultrastructural details of an influenza virus particle, or “virion.”
Giving a lower dose to young children was planned to reduce reactogenicity and febrile convulsions observed with the whole virus vaccines that were in use in the 1970s. But young children have a variable immune response to lower doses, especially against vaccine B strains, they noted (J Ped Infect Dis. 2017 Jan 6. doi: 10.1093/jpids/piw068).
Dr. Jain and coauthors enrolled 2,430 children aged 6-35 months during the 2014-2015 influenza season in the United States and Mexico in this phase III study. Children were randomized into one of two cohorts: one cohort received a standard-doze IIV4 vaccination, while the other received a double-dose. Data on age (6-17 months, 18-35 months), health care center, and influenza primer status also were taken into consideration.
The standard-dose vaccine contained 7.5 mcg of A/California/7/2009 (A/H1N1), A/Texas/50/2012 (A/H3N2), B/Brisbane/60/2008 (B/Victoria), and B/Massachusetts/2/2012 (B/Yamagata), while the double-dose vaccine contained 15 mcg, or twice the amount each, of the same strains. The former was developed by Sanofi Pasteur and the latter by GSK Vaccines.
Primed children who completed the study numbered 1,173; 586 received the standard-dose and 587 received the double-dose. On the unprimed side, 868 completed the study: 442 standard-dose and 426 double-dose. Each dose’s immunogenic noninferiority was quantified by calculating the geometric mean titer (GMT) ratio.
“Immunogenicity was higher in the double-dose group compared with the standard-dose group, particularly against vaccine B strains in children 6-17 months of age and unprimed children,” Dr. Vain and associates said. Both vaccines performed well against the influenza B strain, with the double-dose yielding a GMT of 1.89 against the B/Yamagata strain and 2.13 against the B/Victoria in children aged 6-17 months. Across the entire age spectrum of the study population, unprimed children registered a GMT of 1.85 and 2.04 against the same strains, respectively. For comparison, none of the A strains in any cohort based on age or primed/unprimed registered a GMT above 1.5.
“Increased protection against influenza B [would] be a beneficial clinical outcome [and] use of the same vaccine dose for all eligible ages would also simplify the annual influenza vaccine campaign and reduce cost and logistic complexity,” the authors concluded. “This study provides evidence to support a change in clinical practice to use [double-dose IIV4] in all children 6 months of age and older, once that dosing for a vaccine product has been approved.”
Dr. Jain now is employed by the Bill and Melinda Gates Foundation.
Dr. Jain and several coauthors disclosed ties to GlaxoSmithKline, which funded the study.