FDA Advisers Recommend Overhaul of 2015 Flu Vaccine

Alicia Ault

March 05, 2015

A panel of US Food and Drug Administration (FDA) advisers has recommended two new components for the influenza vaccine for the 2015-16 season.

The influenza vaccine has included the exact same strains for the 2013-2014 and 2014-2015 flu seasons, but data indicate that the vaccine for 2014-2015 has been largely ineffective and that one of the A strains is no longer circulating.

The Vaccines and Related Biological Products Advisory Committee recommended new components for both the trivalent and quadrivalent vaccines that are available in the United States.

The yearly exercise to predict which influenza viruses will be a threat in the upcoming winter is based on global monitoring, but it can be imperfect.

For the winter of 2014-15, the vaccine has proven to be very ineffective, reducing the chances that someone needs to seek medical help for influenza by 19% ― compared with 60% or more in most years ― according to an interim analysis by the Centers for Disease Control and Prevention (CDC).

This season's vaccine mostly failed to protect against the predominant A strain, A/Switzerland/9715293/2013-like virus (H3N2). The H3N2 strains are associated with worse illness and higher mortality.

The Switzerland strain was barely in circulation ― comprising only 1% of viruses detected ― when FDA advisers formulated US vaccine recommendations in February 2014. It was not until late summer that it became apparent that the Switzerland strain was the main illness-causing agent, Lisa Grohskopf, MD, medical officer with the CDC's Influenza Division, told the FDA panel.

The latest data from the World Health Organization (WHO), the Department of Defense, and the CDC indicate that the Switzerland strain continues to be dominant worldwide.

In September 2014, the WHO recommended that an inactivated form of that strain be included in the southern hemisphere vaccine for 2015-16. It also recommended inclusion of the same H1N1 A strain, A/California/7/2009 pandemic09-like virus, and a new B strain, B/Phuket/3073/2013-like virus. For quadrivalent vaccines, the recommendation was to add B/Brisbane/60/2008-like virus.

Both the CDC and the FDA agreed with that recommendation, and the Vaccines and Related Biological Products Advisory Committee followed suit.

Low Effectiveness Hitting Older Americans

The disappointing effectiveness of the vaccine this year has hit older Americans especially hard. There have also been a large number of pediatric cases, and almost 100 deaths in children, said Dr Grohskopf.

Interestingly, for patients older than 65 years, the vaccine effectiveness rate was a bit higher than for other age groups ― 24% overall, compared with 8% for 18- to 49-year-olds and 18% for 9- to 17-year-olds.

For the more deadly H3N2 strain, effectiveness was 28% for those older than 65, and even lower for those aged 6 months to 49 years ― with a low of 12% and a high of 17%.

Those older than 65 have had a much higher rate of hospitalization. There have been at least 14,000 hospitalizations through February 21. For most age groups, hospitalizations were on par with the three previous flu seasons. But for Americans 65 or older, the rate was the highest it has been since the CDC began surveillance of hospitalizations in 2005, said Dr Grohskopf.

Mortality from the flu seems to have peaked just after January 1 but was still above the epidemic threshold as of February 21, she said.

Death due to influenza is a reportable condition in children younger than 18 years, which gives the CDC some good data. As of the latest reporting period, there were 92 deaths, said Dr Grohkopf. Eighty-three of those were associated with influenza A viruses. About half of those were subtyped: all were H3N2 strains.

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