CDC braces for back-to-school flu spike, addresses vaccine worries

Jul 17 2009 (CIDRAP News) – Novel flu activity is still going strong but dropped for the third week in a row, the US Centers for Disease Control and Prevention (CDC) said today during a media briefing that also sought to calm fears about vaccine availability.

Anne Schuchat, MD, director of the CDC's National Center for Immunization and Respiratory Diseases, said the CDC will probably follow the World Health Organization's (WHO's) lead and phase out weekly reports of lab-confirmed cases, which grossly underestimate the true disease burden and divert resources from other pandemic response activities. She said over the next several weeks the agency will start adding new data and other enhancements to its weekly flu report to provide a more detailed profile of the nation's activity.

The CDC's update today, however, reports that the country's number of lab-confirmed cases has reached 40,617, of which 263 were fatal.

In its flu surveillance report for the week ending Jun 11, the CDC said nine states reported widespread activity: California, Delaware, Georgia, Hawaii, Maine, Maryland, Nebraska, New Jersey, and New York. Twelve states and Puerto Rico reported regional influenza activity.

More than 99% of flu isolates that have been subtyped are the novel H1N1 virus, the CDC reported. One of three cases of oseltamivir-resistant viruses detected worldwide was from a child who got sick in California and traveled to Hong Kong. Enhanced antiviral-resistance testing in California has not revealed any oseltamivir-resistant novel H1N1 viruses, the CDC said.

One pediatric death from the new virus was reported during the past week, in a child from Massachusetts. Of the 90 fatal pediatric flu cases that have been reported to the CDC so far this season, 23 were novel H1N1 infections.

Schuchat said the virus might be persisting through the summer, despite the heat and humidity, because of the US population's low immunity to the novel virus rather than because the virus has mechanisms for coping with the conditions. However, she said the CDC doesn't have the data to flesh out its theory about the summer spread.

The CDC expects flu activity to start rising again in September, ahead of the regular flu season, which would coincide with kids congregating in greater numbers as school resumes, she said. The CDC and its partners are in the active stage of planning for a spike in pandemic H1N1 flu activity in early fall, she added.

The CDC's Advisory Committee on Immunization Practices (ACIP) will hold an emergency meeting on Jul 29 to discuss recommendations for which populations should be targeted for novel H1N1 flu vaccination and whether tiering the vaccine prioritization would be appropriate, Schuchat told reporters.

Two federal officials who are involved in high-level vaccine decisions were on hand at the press conference to address recent questions that have cropped up about disappointingly low novel flu vaccine yield and potential international squabbles over vaccine supplies. The officials were Jesse Goodman, MD, the Food and Drug Administration's acting chief scientist and deputy commissioner for scientific and medical programs, and Bruce Gellin, MD, director of the National Vaccine Program, Department of Health and Human Services.

Gellin said federal officials have stockpiled antigen and adjuvant and that National Institutes of Health investigators, as well as researchers at vaccine companies, are starting to test both adjuvanted and nonadjuvanted versions of the novel flu vaccine. Stockpiling the bulk ingredients gives US officials greater flexibility in pulling together a safe and effective vaccine for its citizens, he said.

Schuchat said the CDC has heard concerns about vaccine manufacturers in foreign countries diverting vaccine orders to their own populations. "From our own planning, this is not one of our current concerns," she said. "We haven't received any information that makes us question the supply of what's been promised."

As for poor antigen yields that some manufacturers are reporting for the new virus, Schuchat said the CDC is not surprised and has already incorporated such yields into its planning and vaccine production expectations. "It's within the range of our planning assumptions, but of course there could always be some surprises," she said.

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