HealthDay News — A candidate inactivated quadrivalent influenza vaccine (QIV) is efficacious for preventing influenza in young children, study findings indicate.
“Each year, the annual trivalent influenza vaccine has incorporated only the single B-lineage antigen that is predicted to circulate that season. This choice has led to the B-lineage vaccine being mismatched to the actual circulating B-lineage virus half the time,” Lindsey R. Baden, MD, of Harvard Medical School in Boston wrote in an editorial accompanying the study in New England Journal of Medicine.
To minimize chances of a B-lineage mismatch, the CDC, the Advisory Committee on Immunization Practices and WHO have recently recommended incorporating both B lineages into the annual influenza vaccine. Earlier this year, the FDA approved two quadrivalent influenza vaccines, Fluzone Quadrivalent (Sanofi Pasteur) and Fluarix Quadrivalent (GlaxoSmithKline).
To better elucidate the clinical benefit of quadrivalent vaccines, Varsha K. Jain, MD, MPH, from GlaxoSmithKline Vaccines in King of Prussia, Pa., and colleagues conducted a multinational phase 3 study involving 5,220 healthy children aged 3 to 8 years old.
Participants were randomly assigned to receive a quadrivalent inactivated vaccine (QIV) or hepatitis A vaccine (control). The QIV included 15 μg of hemagglutinin antigen from each of four strains:
- Influenza A/California/7/2009 (H1N1)
- Influenza A/Victoria/210/2009 (H3N2)
- Influenza B/Brisbane/60/2008 (Victoria)
- Influenza B/Florida/4/2006 (Yamagata)
The primary end point was real-time polymerase chain reaction (rt-PCR)-confirmed influenza A or B. Vaccine efficacy was analyzed in the total vaccinated cohort (2,584 children in each group) and in the per-protocol cohort (2,379 in the QIV and 2,398 in the control group).
In the total vaccinated cohort, 563 influenza-like illnesses occurred in 422 children in the QIV group and 657 influenza-like illnesses occurred in 507 children in the control group during the mean 6 month follow-up period.
The researchers found that 2.40% of children in the QIV group and 5.73% in the control group had rt-PCR-confirmed influenza, representing 59.3% QIV efficacy. The attack rate was 0.62% in the QIV group and 2.36% in the control group for moderate-to-severe rt-PCR-confirmed influenza, representing 74.2% QIV efficacy.
In the per-protocol cohort, QIV efficacy was 55.4% and efficacy among children with moderate-to-severe influenza was 73.1%. Compared with the control vaccine, the QIV was associated with reduced risks of a body temperature above 39° C and lower respiratory tract illness in the per-protocol cohort (relative risks, 0.29 and 0.20, respectively).
“These results highlight the potential clinical benefit of administering inactivated influenza vaccines in healthy children,” the researchers wrote.
“Ongoing careful safety assessments of any new therapy, including these vaccines, is essential,” Baden wrote in the editorial. “In the United States, a quadrivalent influenza vaccine with both B-lineage antigens has been introduced this season as an alternative to the traditional trivalent vaccine. Over the next few influenza seasons we hope to see the value of the two Bs.”