MF59-adjuvant influenza vaccine appears effective in infants, young children

Vesikari T. N Engl J Med. 2011;365:1406-1416.

Issue: November 2011

Influenza vaccine with the MF59 adjuvant is efficacious against laboratory-confirmed influenza in infants and young children, according to results of a new study published online today.

Results of the study by Timo Vesikari, MD, and colleagues indicate that MF59-adjuvant vaccine (ATIV) was efficacious against influenza (confirmed by polymerase chain reaction) caused by all circulating influenza strains during two separate study periods (86% efficacy rate), with higher efficacy against vaccine-matched strains (89%).

The researchers investigated the effect of ATIV, an oil-in-water emulsion, on the efficacy of trivalent inactivated influenza vaccine (TIV) in 4,707 healthy children aged 6 months to younger than 72 months who were previously unimmunized with influenza vaccine.

During the 2007 to 2008 season, 654 children were enrolled in Germany, and 2,104 children in Finland were enrolled during the 2008 to 2009 season. Participants were stratified according to age (aged 6 months to younger than 36 months and aged 36 months to younger than 72 months) and were randomly assigned to one of three study groups.

In year 1, patients were assigned to ATIV, subunit TIV or control (non-influenza) vaccine in a ratio of 2:1:1. In the second year of the study, the children were assigned to ATIV, split TIV or control vaccine in a ratio of 2:2:1.

“The subunit influenza vaccine consisted of purified hemagglutinin and neuraminidase viral-surface proteins. The split vaccine consisted of purified disrupted virions. Vaccines were administered in two doses, 28 days apart, with or without concomitant routine vaccines,” according to the researchers.

Attack rates of influenza-like illness across both influenza seasons were 0.7%, 2.8% and 4.7% in the ATIV, TIV and control vaccine groups, respectively. The absolute vaccine efficacy rates against all influenza strains (94 of 110 cases were caused by vaccine-matched H3N2 viruses) were 86% (95% CI, 74-93) for ATIV and 43% (95% CI, 15-61) for TIV.

The relative vaccine efficacy rate for ATIV vs. TIV was 75% (95% CI, 55-87). Among children aged 6 months to younger than 36 months, the efficacy rates for ATIV was 79% (95% CI, 55-90) vs. 40% (95% CI, –6 to 66) for TIV.

For children aged 36 months to younger than 72 months, efficacy rates for ATIV was 92% (95% CI, 77-97) vs. 45% (95% CI, 6-68) for TIV. Antibody responses were higher with ATIV and remained high through day 181, according to the study results.

Regarding adverse events, “The rates of systemic and local reactions to the influenza vaccines with and without the adjuvant were similar in the younger age group (RR=1.04; 95% CI, 0.98-1.09), but systemic events in the older age group were more frequent after administration of ATIV (63%) than after administration of TIV (44%) or the control vaccine (50%),” the researchers wrote, adding that these events were generally mild and of short duration.

Serious adverse events were distributed evenly across the three vaccine groups.

Disclosure: This study was funded by Novartis Vaccines and Diagnostics.

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