Today the Centers for Disease Control and Prevention (CDC) hosted its first Clinician Outreach and Communication Activity (COCA) call since September, focusing on seasonal influenza activity and vaccination, especially the importance of vaccinating children.

“The time to get vaccinated is right now for those 6 months and older. [Flu] rates are increasing,” said Tim Uyeki, MD, MPH, MPP, the chief medical officer of the Influenza Division at CDC. Uyeki said that last year saw high morbidity and mortality with only moderate flu vaccine efficacy (VE). Most important, he said, there was a significant number of severe flu cases among children, with 288 deaths.

“That’s the highest number of deaths we’ve seen since CDC starting tracking this data,” he said.

Last year the CDC confirmed 37 cases of acute necrotizing encephalopathy (ANE), a rapid and severe swelling of the brain following infections. Uyeki said, of the 37 patients, only six (16%) were vaccinated against flu, and the average age of ANE patients was 5 years.

ANE comes on quickly, within two days of flu symptoms, he explained, and 74% of patients end up admitted to intensive care units. Last year, 15 (41%) of the 37 patients with ANE died.

US dominated by H3N2 activity so far

Uyeki said the United States has not yet seen the swift and early flu activity reported by the United Kingdom and Japan, though, like those countries, flu activity is so far dominated by influenza A(H3N2) subclade K.

We have not seen early activity compared to other countries, but cases are now increasing throughout the US.

“We have not seen early activity compared to other countries, but cases are now increasing throughout the US, and influenza H3N2 is increasing and is being reported,” he said. So far of the H3N2 cases subtyped by the CDC this season, 87% are subclade K.

Lisa A. Grohskopf, MD, MPH, also a medical officer in the CDC’s Influenza Division, emphasized that all children six months and older should be vaccinated, and said flu vaccines formulated without thimerosal are preferred.

Thimerosal is a preservative that has been proven safe in countless studies, but it has become a target of anti-vaccine advocates. This summer, the CDC’s Advisory Committee on Immunization Practices voted in favor of using only single-dose influenza vaccines without thimerosal for the current season.

Rise in subclade K in some global regions

In related news, the World Health Organization (WHO), in a global situation report on seasonal flu yesterday, said subclade K infections are rapidly rising in some countries.

“Although global activity remains within expected seasonal ranges, early increases and higher activity than typical at this time of year have been observed in some regions,” the WHO said, noting the rise of subclade K infections.

Both the CDC official and the WHO said preliminary UK data show that the current seasonal vaccine offers strong protection against subclade K.

“Early estimates suggest that the influenza vaccine continues to provide protection against hospital attendance in both children and adults, even though its effectiveness against clinical disease during the current season remains uncertain,” the WHO said.