Slow flu start helps the vaccine effort

Doses will be available through January

In a bad-news year for influenza vaccination, public health authorities are glad for some good tidings: The flu season began slowly and the vaccine promised to be more effective than last year’s mismatched version.

As of mid-November, only Delaware had reported widespread flu activity. New York state and New York City reported regional activity, and elsewhere, influenza remained only sporadic. So far, the influenza vaccine is well-matched with the circulating viruses, A/Fujian/411/2002-like (H3N2) and B/Shanghai/361/2002-like.

Meanwhile, the Centers for Disease Control and Prevention (CDC) continues to redirect flu vaccine supply to the nation’s high-priority populations, including health care workers. Some 2.6 million doses will be available in January, the CDC said.

If vaccine is imported from other countries, it would likely become available in December, said Raymond Strikas, MD, medical officer in the Immunization Services Division of CDC. "We are well aware that the challenges have been very difficult for all of us," he said in a web conference.

In November, CDC began apportioning 7.2 million doses of vaccines to states based on a formula that takes into account the estimated number of people in high-priority categories and the number of doses already shipped to the state. The CDC advised health care providers to contact their state or local health departments if they still have unmet vaccine needs.

Vaccine shortages occurred throughout the country, but within a community, the impact varied greatly. "We’ve had reports of practitioners being next door to each other, one having all the vaccine they expected to get and the other having no vaccine," said Strikas, noting that 33 million doses of Aventis Pasteur’s vaccine already had been distributed when Chiron Corp. announced that it would be unable to provide vaccine this year.

In a worst-case scenario — not enough vaccine and an outbreak of influenza — unvaccinated health care workers can use antivirals — amantadine, rimantadine, and oseltamivir — as chemoprophylaxis, said Tim Uyeki, MD, MPH, of CDC’s influenza branch. They are 70% to 90% effective at preventing influenza illness although they will not necessarily prevent influenza infection, he said. Amantadine and rimantadine only are effective against influenza A viruses, while oseltamivir is effective against both influenza A and B.

"For persons caring for high-risk individuals in an outbreak in a hospital, the duration [of prophylaxis] should be at least for one week following the end of the outbreak," he said.

The CDC will monitor supplies of the antivirals, but "at this time, antiviral supplies are estimated to be adequate," Uyeki noted.

The CDC also is reminding health care workers to use droplet precautions when treating patients with respiratory symptoms and fever, including wearing a mask when they are in close contact with the patients. Droplet precautions should be maintained for five days in otherwise healthy patients and for the duration of their illness with immunocompromised patients.

Rapid antigen diagnostic tests may be falsely negative in up to 30% of cases, the CDC cautioned.

(Editor’s note: More information on influenza vaccine supply and chemoprophylaxis is available from the CDC flu web site: www.cdc.gov/flu.)