It’s Influenza Season Again!

It’s fall, and time to think about getting all of our patients protected from influenza. Although there has been a great deal of media attention on the influenza A (H5N1) avian influenza virus in southeast Asia, our patients face a much greater immediate threat from the good old-fashioned influenza strains that circulate every year in San Diego. The San Diego Health and Human Services virology laboratory has already isolated both influenza A and influenza B strains in San Diego this fall.

CDC estimates that 5–20 percent of Americans come down with influenza each season, which typically lasts from November to March. Although most people recover, CDC estimates that in the United States more than 200,000 people are hospitalized and about 36,000 people die from influenza and its complications each year. Influenza viruses cause disease among all age groups. Rates of infection are highest among children, but rates of serious illness and death are highest among persons aged > 65 years, children aged < 2 years, and persons of any age who have medical conditions that place them at increased risk for complications from influenza.

As part of CDC’s influenza surveillance program, about 80 World Health Organization (WHO) and 50 National Respiratory and Enteric Virus Surveillance System (REVSS) collaborating laboratories located throughout the United States report the total number of respiratory specimens tested and the number positive for influenza types A and B each week. A recent CDC study demonstrated that influenza-associated hospitalizations during an influenza season are highest when influenza A (H3N2) viruses predominate compared to years when influenza A (H1N1) or influenza B viruses predominate.

The best protection against influenza is immunization. The 2005–06 trivalent vaccine virus strains are A/California/7/2004 (H3N2)-like, A/New Caledonia/20/99 (H1N1)-like, and B/Shanghai/361/2002-like antigens. These strains are incorporated into both the traditional trivalent inactivated vaccine (TIV) and also into the newer live attenuated influenza vaccine (LAIV). LAIV was approved in 2003. This nasal-spray vaccine contains attenuated live viruses and is approved for use only among healthy people between the ages of 5 and 49 years.

Although some offices and hospitals are still waiting for their full shipment of influenza vaccine this year, CDC is still estimating that we will have sufficient vaccine for those who should be immunized. The United States has an additional influenza vaccine manufacturer this year (GlaxoSmithKline) and the return of the manufacturer that was unable to produce vaccine last year (Chiron). Our overall supply of vaccine is significantly better than during the 2004–2005 season. Additional vaccine is being shipped throughout the month of November and may arrive later than you initially expected. You are encouraged to immunize your patients into January since influenza often doesn’t peak in San Diego until February.

As of October 24, 2005, there are no restrictions recommended for the delivery of influenza vaccine. Here is a reminder of the primary priority groups for influenza immunization:

• persons aged 50 years and older, with and without chronic health conditions
• residents of long-term care facilities
• persons aged 2–64 years with chronic health conditions
• children aged 6–23 months
• pregnant women
• healthcare personnel who provide direct patient care
• household contacts and out-of-home caregivers of children aged < 6 months
• household contacts of persons at high risk for complications from the flu

In addition to the routine recommendations above, the following new strategies have been incorporated into CDC’s recommendations this year:

• Persons with any condition (e.g., cognitive dysfunction, spinal cord injuries, seizure disorders, or other neuromuscular disorders) that can compromise respiratory function or the handling of respiratory secretions or that can increase the risk for aspiration should be vaccinated against influenza.
• Special emphasis is being placed on assuring that all healthcare workers are vaccinated and that facilities that employ healthcare workers be strongly encouraged to provide vaccine to workers by using approaches that maximize immunization rates.
• Use of both available vaccines (TIV and LAIV) is encouraged for eligible persons every influenza season, especially persons in recommended priority groups. During periods when inactivated vaccine is in short supply, use of LAIV is especially encouraged when feasible for eligible persons, including healthcare workers.

I want to make sure everyone takes note of the emphasis on immunizing healthcare workers. Influenza immunization rates for healthcare workers are poor, with a national estimate that < 50 percent of healthcare workers receive an annual influenza immunization. This despite the fact that we know healthcare workers can spread influenza in their offices and in hospitals. A new CDC-sponsored project, the San Diego Hospital Influenza Immunization Project, is providing an opportunity for San Diego to lead by example. Coordinated by the San Diego HHSA Immunization Branch, this project is working with a large number of San Diego hospitals to develop innovative strategies to get our hospital-based healthcare workers immunized. Stay tuned for what is learned during this exciting project. In the meantime, get your flu shot!

The other important message for your patients is that personal measures such as good hand washing habits and avoiding crowds when ill can help protect them and others. This advice includes not going to work when ill, and this applies to healthcare workers as well. We don’t want to be the ones transmitting influenza in our offices.

A number of resources are available for more information on influenza. The following websites have both local and national information on the current influenza season and vaccine supply.

• www.immunization-sd.org/home.html
• www.cdc.gov/flu

In addition, inform your patients about the Community Health Improvement Partners (CHIP) Immunize San Diego website (www.sdchip.org/immunize.html) for information on local sites where influenza vaccine is available. For recorded information about influenza vaccine availability and clinic locations, please call the County Flu Information Line at (866) 358-2966 or the Aging and Independence Services/Community Health Improvement Partners Flu Hotline at (877) 358-0202.