The trial also suggests that the vaccine can prevent children against "moderate to severe" flu, with an efficacy of more than 70% in those cases.
One of the main questions remains about the quadrivalent vaccine; whether or not it can protect against influenza B. The 2012-13 influenza season was exacerbated by a late surge of influenza B infections. The trivalent vaccine contains two strains of influenza A and one strain of influenza B. Whereas, the quadrivalent vaccine contains two A and two B strains. Hopefully by next spring/summer there will be enough data to draw conclusions on how effective the quadrivalent vaccine was against influenza B.
The trial was sponsored by GSK, which achieved US Food and Drug Administration (FDA) approval of FluLaval Quadrivalent in August 2013. The company also makes a second 4-strain flu vaccine, Fluarix Quadrivalent.
5,220 Children in Eight Countries
The trial was conducted at 15 centers in Bangladesh, the Dominican Republic, Honduras, Lebanon, Panama, the Philippines, Thailand, and Turkey. The authors recruited 5,220 children from ages three to eight and assigned them to receive the Quadrivalent Influenza Vaccine (QIV) or a hepatitis A vaccine as a control.
The QIV targeted influenza A/H1N1 (2009) and A/H3N2 as well as the two B strains. The QIV group consisted of 2,584 children and the control group of an equal number. Members of the treatment group received one or two doses, depending on their vaccine priming status.
Recruitment of the children began in December 2010, and the authors conducted active and passive surveillance for flu-like illness for at least six months, through the end of October 2011. The trial's primary end point was influenza A or B confirmed by quantitative real-time polymerase chain reaction (qRT-PCR). As secondary end points, the authors used PCR-confirmed moderate-to-severe flu and PCR-positive, culture confirmed flu. Moderate-to-severe illness was defined as a body temperature above 39 degrees C, acute otitis media, lower respiratory tract illness, or serious extrapulmonary complications.
As for safety, the report says there were no notable differences between the QIV group and the control group, except that pain at the injection site was more common in the QIV group (47.7% versus 34.8%)
The authors note that there is limited evidence from randomized trials to support the use of inactivated flu vaccines in healthy children. They say their results are in line with those of three other randomized trials of trivalent inactivated vaccines: 43% efficacy in children six months to six years old, 51% in children 18 months to six years, and 56% in children three to nine years (H1N1 only).
This randomized study provides additional evidence of the efficacy of QIV against influenza as confirmed by PCR, the researchers say. They stress the vaccine's efficacy against moderate and severe cases, saying the greatest value of vaccination is in preventing such cases.
Lance D. Presser has a PhD in Microbiology and Immunology and currently is a Public Health Laboratorian