News Scan for Jun 12, 2019

News brief

DOD researchers tease out differences in cell- and egg-based flu vaccines

A Department of Defense (DOD) study that compared vaccine effectiveness (VE) of cell-based and egg-based flu vaccines found that the egg-produced version performed significantly better against the 2009 H1N1 strain, and the cell-based version performed better against H3N2, though the difference wasn't statistically significant. Researchers published their findings yesterday in Vaccine.

The DOD Global Respiratory Pathogen Surveillance Program and other groups have been assessing the effectiveness of different flu vaccine formulations, especially against the backdrop of declining estimates for H3N2 due to egg-adapted genetic substitutions and a host of other factors that might affect vaccine performance.

The test-negative case-control design study took place among DOD beneficiaries who were seen for flulike illness from Oct 1, 2017, through Apr 28, 2018. The DOD had bought more cell-based vaccine than egg-based vaccine for the season: 57% was Flucelvax, and the rest was egg-based (FluLaval and Fluarix).

The analysis included 1,757 confirmed flu cases and 2,280 test-negative controls. Overall, both vaccines were moderately protective against all flu types: 46% for cell-based and 53% for egg-based. The researchers found that both vaccines performed best against the 2009 H1N1 strain; VE for cell-based vaccine was moderately high in adults at 71% and moderate in children at 56%, and VE for egg-based vaccine was 81% in adults and 88% in children.

When the team compared the VE of the two vaccines against each other, results were significant only for 2009 H1N1, which favored the egg-based vaccine with odds ratios of 2.0 for all dependents and 2.9 for children. For the H3N2 analysis, the investigators found no statistical significance, though the odds favored the cell-based vaccine.

The researchers note more studies are needed to better evaluate differences between cell- and egg-based vaccines and that future studies should focus on specific subtypes and span multiple seasons.
Jun 11 Vaccine abstract


Study: Flu vaccine in resource-poor areas offers direct, indirect protection

A study today in The Lancet Global Health suggests that pediatric influenza vaccination offers varying levels of protection for recipients and unvaccinated household family members.

The clustered, controlled study took place in three villages in India among children ages 6 months to 10 years between 2009 and 2012. Families were randomly assigned to either intramuscular trivalent inactivated influenza vaccine (IIV3) or a control of inactivated poliovirus vaccine (IPV), with vaccination occurring annually for 3 years. During the study period, researchers vaccinated 4,345 children (2,132 with IIV3 and 2,213 with IPV) from 1,868 households that contained 10,813 unvaccinated household contacts.

The total vaccine efficacy against laboratory-confirmed influenza over the 3-year period was 45.1% (95% confidence interval (CI), 35.2% to 53.5%). The vaccine was most effective in year 3 of the study (74.2%; 95% CI, 57.8% to 84.3%), and lowest in year 1 (25.6%; 95% CI, 6.8% to 40.6%). In year 3, researchers also saw a significant indirect protection (vaccine efficacy 38%; 95% CI, 7.4% to 58.6%) among unvaccinated family members.

"Significant household-level indirect protection was observed during 1 year of high direct protection and should be considered as a potential effect of vaccination," the authors concluded.

In a commentary on the study, Maharaj Kishan Bhan, MBBS, MD, and Bireshwar Sinha, MBBS, MD, two Indian experts who weren't involved in the study, pointed out that the varying protection levels provide more rationale for a universal flu vaccine, which would be especially useful in a resources-limited community.

"The current influenza vaccines are moderately efficacious and cumbersome to manufacture," Kishan Bhan wrote. "A universal influenza vaccine that is efficacious against all strains of this virus is a goal worthy of pursuit."
Jun 12 Lancet Glob Health study
Jun 12 Lancet Glob Health commentary

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