New Phase III Study Shows Significantly Greater Efficacy in Children 6-24 Months Who Receive Adjuvanted Influenza Vaccine (aQIV)

aQIV demonstrates additional clinical benefit over non-adjuvanted QIV influenza vaccine in children aged 6 to less than 24 months

RIGA, Latvia--()--Annual influenza-related hospitalizations among U.S. children younger than the age of 5 have ranged from 7,000 to 26,000 since 2010, and annual reported influenza-related deaths in children have ranged from 37 to 171 during regular influenza seasons in the same time span, according to the U.S. Centers for Disease Control and Prevention (CDC).1 One potential solution to reducing these hospitalizations and deaths is with a more effective vaccine for children.

In a recently completed phase III study, an adjuvanted influenza vaccine (aQIV) that protects against four strains of influenza (aQIV) induced a superior immunogenic response in children aged 6 months to less than 6 years relative to a comparator non-adjuvanted quadrivalent influenza vaccine, including the significantly drifted strain that circulated during the 2014-2015 season.2 aQIV provided additional clinical benefit over non-adjuvanted influenza vaccine in children aged 6 to less than 24 months, manifested by significantly greater relative efficacy (31 percent) and the largest relative increase in immunogenicity compared with older children.2

“One challenge to lowering pediatric hospitalization rates is that the effectiveness of currently licensed influenza vaccines is uncertain in young children, especially those under the age of 2,” said Dr. Timo Vesikari, MD, PhD, University of Tampere Medical School. “As a result, vaccines that are more effective in preventing influenza in this age group, like the MF59-adjuvanted quadrivalent influenza vaccine (aQIV), are desirable.”

In vaccine-naïve children aged 6 months to less than 6 years who receive two dosages of aQIV, aQIV was significantly more efficacious (55 percent) than the non-adjuvanted comparator in preventing influenza prior to the second dose of vaccine.2 This revealed another potential benefit of aQIV: improved protection from influenza after a single vaccine dose. The overall vaccine safety profiles were similar except for the expected higher incidence of solicited adverse events after vaccination with aQIV.2

“Influenza and its complications pose a serious public health threat to young children, especially those under 2 years of age,” Dr. Vesikari said. “Because standard influenza vaccines are less efficient in producing a robust immune response in young children, improved vaccines are urgently needed. Our study demonstrated that aQIV represents an important new opportunity to introduce a potentially improved influenza vaccine option.”

About the Phase III Study

The phase III study was led by Dr. Vesikari and sponsored by Seqirus during the 2013-2014 and 2014-2015 influenza seasons. The study involved 10,612 children aged 6 months to less than 6 years who received one or two doses of aQIV or a non-adjuvanted influenza vaccine.

Endpoints included RT-PCR confirmed, culture-confirmed and antigenically matched influenza, and immunogenicity against homologous and heterologous strains of influenza A and/or B. Significant relative vaccine efficacy was demonstrated in children 6 to less than 24 months of age but not in the overall study population. All endpoints were pre-specified for both overall age group and the subgroup aged 6 to less than 24 months.2

Dr. Vesikari will present the findings as a late-breaking poster presentation at the Sixth ESWI Influenza Conference in Riga, Latvia.

About Seqirus

Seqirus is part of CSL Limited (ASX:CSL), headquartered in Melbourne, Australia. The CSL Group of companies employs more than 20,000 people with operations in more than 60 countries.

Seqirus was established on July 31, 2015 following CSL’s acquisition of the Novartis influenza vaccines business and its subsequent integration with bioCSL. As the second largest influenza vaccine provider in the world, Seqirus is a major contributor to the prevention of influenza globally and a transcontinental partner in pandemic preparedness.

Seqirus operates state-of-the-art production facilities in the US, the UK and Australia, and manufactures influenza vaccines using both egg-based and cell-based technologies. It has leading R&D capabilities, a broad portfolio of differentiated products and a commercial presence in more than 20 countries.

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  1. National Center for Immunization and Respiratory Diseases. “Flu Vaccine for Preteens and Teens.” Available at:
  2. Timo Vesikar, MD, PhD, Judith Kirstein, MD, CPI, Grace Devota Go, MD, FPPS, FPIDSP, RN, Brett Leav, MD, Mary Ellen Ruzycky, RN, MS, Leah Isakov, PhD, MBA, Marianne De Bruijn, PhD, Janine Oberye, MSc, Esther Heijnen, MD, PhD. “Efficacy, Immunogenicity and Safety of MF59 Adjuvanted Quadrivalent Influenza Vaccine Compared to a Nonadjuvanted Licensed Influenza Vaccine in Children Aged 6 Months to 6 Years: A Randomized, Controlled, Observer-Blind Clinical Trial.” In: Sixth ESWI Influenza Conference; 2017 Sept 10-13; Riga, Latvia. Abstract nr V118_05.

Seqirus is a CSL Limited company. ASX:CSL ABN: 26 260 735 035 US/aQIV/0917/0016


For Seqirus:
Dani Jurisz, +1 612-455-1726

Release Summary

New phase III study shows significantly greater efficacy in children 6-24 months who receive adjuvanted influenza vaccine.


For Seqirus:
Dani Jurisz, +1 612-455-1726