An investigational quadrivalent flu vaccine formulated to be less pyrogenic had noninferior immunogenicity, compared with a U.S.-licensed vaccine, in children aged 5-17 years, Jolanta Airey, MD, of Seqirus in Parkville, Australia, and her associates reported.

In 2010, in Australia and New Zealand, use of a trivalent flu vaccine was associated with unexpected reports of fever and febrile seizures in children aged younger than 9 years. Research into the issue suggested that “degraded RNA fragments delivered by residual lipids activated the release of proinflammatory cytokines, which stimulated the pyrogenic response in children,” the study authors noted. “Increasing the level of sodium taurodeoxycholate (TDOC) to split the B strain in particular resulted in decreased levels of residual lipids and attenuated proinflammatory cytokine signals.”

That led to development of an inactivated, split-virion quadrivalent flu vaccine with the following strains: Type A (H1N1)-like virus, Type A (H3N2)-like virus, Type B (Victoria lineage), and Type B (Yamagata lineage), split at 1.5% with TDOC. It also led to a study to discover how this quadrivalent flu vaccine, called IIV4, held up in relation to a comparator U.S. licensed quadrivalent flu vaccine, called comparator IIV4.

In a phase III, randomized, observer-blinded study of the two flu vaccines at 32 centers in the United States between September 2015 and June 2016, 1,709 children aged 5-17 years received IIV4, and 569 children the same age received comparator IIV4 (Fluarix Quadrivalent). The two vaccines generated strong immune responses against all the vaccine strains in the children, with the hemagglutination inhibition geometric mean titers similar for all strains and higher for A strains than B strains for both vaccines.

In the 5- to 8-year-old group, fever was reported by 4.5% of those in the IIV4 group and 3.6% of children in the comparator IIV4 group (relative risk, 1.22). In the 9- to 17-year-old group, fever was reported by 2.1% of children in the IIV4 group and 0.8% of those in the comparator IIV4 group (RR, 2.80). Severe fever was reported by 1% or less of any of the groups of children.

Read more in the journal Vaccine ( 2017 May 9;35[20]:2745-52 ).