News from the FDA/CDC

Drop in flu activity suggests season may have peaked



Influenza activity dropped during the week ending Feb. 15, according to the Centers for Disease Control and Prevention. That decline, along with revised data from the 2 previous weeks, suggests that the 2019-2020 season has peaked for the second time. The rate of outpatient visits for influenza-like illness (ILI) came in at 6.1% for the week ending Feb. 15, after two straight weeks at 6.7%, the CDC’s influenza division reported Feb. 21.

The rates for those 2 earlier weeks had previously been reported at 6.8% (Feb. 8) and 6.6% (Feb. 1), which means that there have now been 2 consecutive weeks without an increase in national ILI activity.

State-level activity was down slightly as well. For the week ending Feb. 15, there were 39 states and Puerto Rico at the highest level of activity on the CDC’s 1-10 scale, compared with 41 states and Puerto Rico the week before. The number of states in the “high” range, which includes levels 8 and 9, went from 44 to 45, however, CDC data show.

Laboratory measures also dropped a bit. For the week, 29.6% of respiratory specimens tested positive for influenza, compared with 30.3% the previous week. The predominance of influenza A continued to increase, as type A went from 59.4% to 63.5% of positive specimens and type B dropped from 40.6% to 36.5%, the influenza division said.

In a separate report, the CDC announced interim flu vaccine effectiveness estimates.For the 2019-2020 season so far, “flu vaccines are reducing doctor’s visits for flu illness by almost half (45%). This is consistent with estimates of flu vaccine effectiveness (VE) from previous flu seasons that ranged from 40% to 60% when flu vaccine viruses were similar to circulating influenza viruses,” the CDC said.

Although VE among children aged 6 months to 17 years is even higher, at 55%, this season “has been especially bad for children. Flu hospitalization rates among children are higher than at this time in other recent seasons, including the 2017-18 season,” the CDC noted.

The number of pediatric flu deaths for 2019-2020 – now up to 105 – is “higher for the same time period than in every season since reporting began in 2004-05, with the exception of the 2009 pandemic,” the CDC added.

Interim VE estimates for other age groups are 25% for adults aged 18-49 and 43% for those 50 years and older. “The lower VE point estimates observed among adults 18-49 years appear to be associated with a trend suggesting lower VE in this age group against A(H1N1)pdm09 viruses,” the CDC said.

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