Quadrivalent Influenza Vaccine Safe and Effective for Children 6 Months-5 Years Old

Although COVID-19 has been the most frequently discussed respiratory virus for the past couple of years, seasonal influenza is coming back in full force.

Young children are at heightened risk of severe influenza and related complications, according to the American Academy of Pediatrics. To ensure the best protection for this high-risk demographic, CSL Seqirus tested the safety and immunogenicity of their cell-based quadrivalent inactivated influenza vaccine (QIVc) in children 6 months to 5 years of age.

The results of this phase 3 clinical study were published this week in Pediatrics. The randomized, observer-blind, comparator-controlled, multicenter study was conducted during the Northern Hemisphere’s 2019-2020 flu season.

The QIVc was compared against a US-licensed influenza vaccine (QIV). The children enrolled in the trial were randomized 2:1 to receive the QIVc or QIV. They received either 1 or 2 doses, depending on their influenza vaccination history.

The currently approved influenza vaccines protect against 2 type A subtypes and 2 type B-lineage viruses. Pediatric populations experience a high burden of type B infections, with a disproportionate number of type B deaths. Thus, there is a need for updated vaccines with expanded protection against both type B viruses.

Investigators assessed safety for 180 days after the last vaccine was administered and sera were collected, as well as 28 days after last vaccination to measure antibody titers in hemagglutination inhibition and microneutralization assays. They evaluated immunogenicity of the two vaccines with 1092 participants in the QIVc cohort and 575 participants in the QIV cohort. They reported a successful criteria was met for strains used for the vaccines.

The data showed that the following: “the geometric mean titer ratios (upper bound 95% CI) were A/H1N1, 0.73 (0.84); A/H3N2, 1.04 (1.16); B/Yamagata, 0.73 (0.81); and B/Victoria, 0.88 (0.97). Seroconversion differences (upper bound 95% CI) were −11.46% (−6.42), 3.13% (7.81), −14.87% (−9.98), and −5.96% (−1.44) for A/H1N1, A/H3N2, B/Yamagata, and B/Victoria, respectively.”

They also reported that adverse effects were similar between the two cohorts and there were no serious adverse events. “QIVc was well-tolerated and immune responses were similar to a US-licensed QIV in children 6 through 47 months of age,” the investigators concluded.