A quadrivalent influenza vaccine could offer some important advantages over other influenza vaccines, and in clinical trials, was nearly equal to that of two trivalent vaccines for children aged 2 to 17 years, according to results in a recently published study.
“Influenza B strains account for an average of 25% of overall influenza infections in the last decade. The previously available trivalent influenza vaccines have only targeted one B subtype, either Yamagata or Victoria. And as would be expected, for the past 10 years (2001 to 2011), we have been correct only 50% of the time,” said Infectious Diseases in Children Editorial Board member Stan L. Block, MD. “So why not target both influenza B subtypes and make a quadrivalent influenza vaccine by including both B Yagamata and B Victoria strains, along with the customary two A subtypes?”
Block and colleagues compared post-dose geometric mean titers of hemagglutination inhibition antibodies from a group of 2,312 children who received the quadrivalent vaccine or one of two trivalent vaccines.
Children randomly received on a 3:1:1 basis either the quadrivalent vaccine, which contained the Ann Arbor strain live-attenuated influenza (Q/LAIV) or one of two trivalent vaccines that each had a B strain from a different lineage (T/LAIV). Block and colleagues said the overall results of the various study groups were comparable when it came to immunogenicity and safety, with one exception: Children aged 2 to 8 years were more prone to fever after the first dose of Q/LAIV (5.1% vs. the T/LAIV group’s 3.1%).
“Q/LAIV induced robust antibody titers to influenza B strains from both lineages, but the trivalent vaccines each induced robust antibody titers only to B strains from the homologous lineage,” the study researchers wrote.
They said the use of Q/LAIV has the potential to provide additional protection when trivalent vaccines contain a mismatched B virus that is responsible for most of the influenza B disease. This has occurred in five of the most recent 10 influenza seasons (2001-2002 to 2010-2011), according to the study findings.
“The influenza virus is a crafty organism. Although two influenza types infect humans (A and B), both types have two distinct subtypes — A has H1N1 and H3N2 subtypes, and B has Yamagata and Victoria subtypes. Even within the A and B subtypes, vaccine-type drifted antigenic variants are commonly encountered every year or two. This can render the annual flu vaccine less effective,” Block told Infectious Diseases in Children.
He said the Q/LAIV should have some important pediatric advantages over the influenza vaccine, including:
- LAIV has shown longer durability during the same season and even the second season (55%) without a booster.
- A single dose of LAIV is highly protective in vaccine-naive children (65% to 87% vs. 0% to 20%).
- LAIV has demonstrated better efficacy against antigenic drift among A subtypes.
- Most children prefer not to receive a shot.
- The vaccine has both B subtypes covered.
The downside, Block said, is that LAIV is not approved for children aged 6 to 24 months. Fluzone (Sanofi-Pasteur) is the only influenza formulation approved for use in children in that age group. In addition, LAIV use in children with recent asthma/wheezing or chronic illnesses is still controversial and a precaution.
Block said there is more good news on the horizon for pediatrics: “We have completed testing on a quadrivalent formulation of Fluzone and a totally different cell-culture (not-egg containing) formulation of flu shot (Optaflu, Novartis).”
Disclosure: Dr. Block reports receiving vaccine research grants from MedImmune, Novartis and Sanofi.