MADRID – An intramuscular inactivated quadrivalent influenza vaccine reduced the risk of laboratory-confirmed influenza by up to 69% in previously unvaccinated children aged 6-35 months in a large randomized trial, Stephanie Pepin, MD, reported at the annual meeting of the European Society for Paediatric Infectious Diseases.
The trial included 5,806 healthy 6- to 35-month-olds. More than 5,400 of them were randomized to two full 0.5-mL intramuscular doses of the quadrivalent vaccine or placebo given 28 days apart, while the remaining 316 children received an older trivalent influenza vaccine. The study was conducted during four distinct influenza seasons in Europe, Asia, South America, and Africa between March 2014 and September 2016, explained Dr. Pepin of Sanofi Pasteur in Marcy L-Etoile, France.
The quadrivalent influenza vaccine (QIV) is licensed by the Food and Drug Administration as Fluzone Quadrivalent for use in patients as young as 6 months of age. It contains two A- and two B-lineage influenza strains in order to address the common problem of mismatches between circulating influenza B and the single B-lineage strain included in trivalent vaccines.
The incidence of any laboratory confirmed strain of influenza illness during the period from 14 days post-vaccination to the end of flu season was 4.72% in the QIV group, compared with 9.84% in controls who received placebo, which translated to 52% efficacy. The incidence of influenza from vaccine-similar strains as determined by the Sanger sequencing method was 1.01% in children randomized to QIV, compared with 3.28% with placebo, for a 69% efficacy rate.
The QIV had a safety profile in this young population that was similar to the older licensed trivalent vaccine. The most frequently reported adverse reactions to the QIV were injection site pain, irritability, loss of appetite, abnormal crying, and malaise, each reported in 19%-25% of children after the first injection and in 14%-18% after the second. These were typically mild grade 1 or 2 reactions, which arose in the first 3 days after vaccination and resolved spontaneously 1-3 days later.
The trial was sponsored by Sanofi Pasteur and presented by a company employee.