according to an industry-funded synthesis of six studies.
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The vaccine “offers significant advances over conventional inactivated influenza vaccines and presents an acceptable safety profile in children 6 months through 5 years of age,” Sanjay S. Patel, PhD, of Novartis Vaccines and Diagnostics, Cambridge, Mass., and associates wrote in the analysis, published in the International Journal of Infectious Diseases. “The noteworthy increases in antibody responses and decreases in influenza cases following vaccination suggest an alternative for use in a population that is heavily impacted by influenza disease.”
Children are, of course, vulnerable to flu. The Centers for Disease Control and Prevention reported that 186 children died of flu during the landmark 2017-2018 flu season. That’s the highest number of pediatric flu deaths since they became a notifiable condition in 2004 (exclusive of the 2009 pandemic, when 358 pediatric deaths were reported from April 15, 2009, to October 2, 2010).The CDC said the vaccine during that flu season had an overall effectiveness level of 40%. According to research of others, however, flu vaccines are less effective in younger children than in adolescents and adults (Vaccine. 2014;32[31]:3886-94; Cochrane Database Syst Rev. 2008. doi: 10.1002/14651858.CD004879.pub3).
Fluad – a MF59-adjuvanted inactivated trivalent seasonal influenza vaccine – is used in adults over 65 in the United States and 29 other countries, and it is approved for children aged 6 months through 23 months in Canada.
Dr. Patel and associates examined the results of six studies – one phase 1b, three phase 2, and two phase 3 – that tested Fluad with or without other vaccines in 11,942 children aged 6 months to 5 years. The studies, mostly multicenter, were conducted in various countries, mainly in Europe and South and Central America, from 2006 to 2012.
In general, children in the intervention groups in the studies received two doses of the Fluad vaccine 4 weeks apart: two 0.25-mL doses for children aged 6-35 months and two 0.5-mL doses for those aged 3 years or older. In most of the studies, parallel control groups received nonadjuvanted trivalent or quadrivalent influenza vaccines.
Most participants (93%-94%) completed the studies. Solicited adverse effects were common in all groups (72% in the Fluad group vs. 67% who received IIV3 vaccines), and generally mild to moderate and resolved in 1-3 days. Unsolicited adverse effects were similar (55% and 62%, respectively) in the two flu vaccine groups. The authors wrote that “these data reflect a safety profile consistent with other licensed inactivated influenza vaccines administered to children.”
As for results, Dr. Patel and colleagues said, “HI [hemagglutination inhibition] antibody responses to both homologous and heterologous influenza strains are higher following vaccination with aIIV3, and this increase in immunogenicity is observed across all age subgroups in children aged 6 months through 5 years, and most profound in the children 6 to 36 months.”
For example, in one of the phase 3 studies when the influenza viruses were antigenically matched (homologous) for A/H1N1 among the children aged 6-35 months seroconversion was 100% for allV3 (Fluad) and 38% for IIV3-1/IIV3-4 (trivalent/quadrivalent flu vaccines); among children aged 3-5 years seroconversion was 100% for allV3 and 82% for IIV3-1/IIV3-4. For AH3N2 homologous among children aged 6-35 months, seroconversion was 98% for allV3 and 44% for IIV3-1/IIV3-4. For the B strain homologous among children aged 6-35 months, seroconversion was 88% for allV3 and 19% for IIV3-1/IIV3-4; among children aged 3-5 years seroconversion for B was 99% for allV3 and 59% for IIV3-1/IIV3-4.
In the same study when the influenza viruses were antigenically mismatched (heterologous) for A/H1N1 among children of all ages 6 months to greater than 72 months, seroconversion was 96% for allV3 (Fluad) and 44% for IIV3-1/IIV3-4; for A/H3N2 it was 98% for allV3 and 49% for IIV3-1/IIV3-4, and for the B strain it was 10% for allV3 and 3% for IIV3-1/IIV3-4.
They added that “in addition, aIIV3 had the fastest onset of immunogenicity and longest persistence of immune response, which has implications for the real-world clinical setting, where the influenza season might start earlier than expected or last longer, and second (follow-up) vaccinations may be missed.”
Dr. Patel and associates said the MF59 adjuvant in Fluad “recruits immune cells (primarily monocytes, macrophages, neutrophils, and dendritic cells) at the site of injection and differentiates them into antigen-presenting cells. With an MF59-adjuvanted vaccine, more antigen is transported from the injection site to the draining lymph node, wherein MF59 leads to T-cell activation and an increased B-cell expansion and a greater number and diversity of antibodies.”
According to goodrx.com, one syringe of Fluad 0.5 mL costs $45-$74 with coupon. The same dose of Fluzone Quadrivalent, a flu vaccine recently approved by the Food and Drug Administration for use in young children aged 6-35 months, costs $31 with coupon.
The study was funded by Novartis Vaccines and Diagnostics and Seqirus (formerly part of Novartis Vaccines and Diagnostics). The study authors disclosed employment by Novartis and Seqirus.
SOURCE: Patel SS et al. Int J Infect Dis. 2019. doi: 10.1016/j.ijid.2019.05.009.