Cell-based flu vaccine effective among children in randomized trial

A cell-based influenza vaccine was 54% effective among children during three recent influenza seasons and provided protection regardless of previous vaccination status, according to the results of a randomized clinical trial.

Most influenza vaccines — including approximately 82% of this year’s U.S. supply — are still manufactured using egg-based technology. These vaccines prevent disease, but their effectiveness is “frequently suboptimal,” researchers on the new international, multi-institution study wrote in The New England Journal of Medicine. The reduced effectiveness has been linked to adaptations resulting from the production method.

Vaccines based on viruses grown in a cell culture instead of an egg have shown promise. Only one cell-based vaccine, Flucelvax Quadrivalent (IIV4c, Seqirus), is approved for use in the U.S. A previous phase 3 trial demonstrated that the vaccine was well tolerated and immunogenic in children, “but the efficacy of the vaccine against clinical influenza disease in children and adolescents has not been confirmed in a randomized clinical trial,” researchers wrote in the new study.

They tested IIV4c in a phase 3/4 trial to determine its effectiveness among more than 4,500 children and adolescents aged between 2 and 18 years who were randomly assigned to receive either the influenza vaccine or a meningococcal vaccine. The study took place in eight countries over the course of the 2017 Southern Hemisphere influenza season and the 2017-2018 and 2018-2019 Northern Hemisphere influenza seasons.

Of the 4,509 participants, 65.9% had received an influenza vaccine prior to the study, and 50.7% were between the ages of 2 and 9 years.

Following the inoculation, researchers phoned participants weekly during each season, asking for reports on influenza-like symptoms like fever, cough, sore throat, rhinorrhea or nasal congestion. Those who reported symptoms were then swabbed and tested for influenza A/H1N1, A/H3N2, and B.

Of the 4,509 pediatric participants in the cohort, 1,576 reported influenza-like systems from more than 2 weeks after their vaccination to the end of the season, with 539 being confirmed as having laboratory-tested influenza.

Altogether, IIV4c was found to be 54.6% effective overall against confirmed influenza (95% CI, 45.7%-62.1%), including 80.7% effective against influenza A/H1N1 (95% CI, 69.2%-87.9%), 42.1% effective against influenza A/H3N2 (95% CI, 20.3%-57.9%), and 47.6% effective against influenza B (95% CI, 31.4%-60%).

Efficacy against any culture-confirmed strain regardless of antigenic match was 60.8% (95% CI, 51.3%-68.5%). Against antigenically matched strains, it was 63.6% (95% CI, 53.6%-71.5%).

“Influenza vaccine manufacturing platforms that do not rely on eggs offer certain advantages, including avoidance of egg-adaptive hemagglutinin mutations and a shorter response time when a new influenza virus emerges,” the researchers wrote.