Flu Season 2000-01

 Back to Story

FLU VACCINE SUPPLY Q & A By  U.S. Centers for Disease Control and Prevention

Will there be a delay in the availability or shortage of influenza vaccine this fall?
At this time, delays in the distribution of influenza vaccine are expected for the 2000-2001 influenza season. It is also possible that significantly fewer doses of influenza vaccine might be available for distribution than last year.

How much of an influenza vaccine shortage could there be?
Last season, approximately 80-85 million doses of influenza vaccine were produced for distribution in the United States. The exact number of doses that will be produced this year is uncertain at this time. The situation will be continuously assessed and more precise estimates of the influenza vaccine supply will be available in the future.

When will you know how much of a delay or shortage will occur?
The amount of influenza vaccine and timing of availability should become clearer over the next two months. As new information becomes available, CDC and FDA will issue updates.

Who are the manufacturers licensed to distribute influenza vaccine in the U.S.?
The four companies are Parkedale Pharmaceuticals, Inc., Rochester, Michigan; Wyeth-Ayerst Laboratories, Inc., Marietta, Pennsylvania; Aventis Pasteur, Swiftwater, Pennsylvania; and Medeva Pharma Ltd., United Kingdom.

What is the cause of the potential delay and potential shortage of influenza vaccine?
First, some influenza vaccine manufacturers have reported that one of the three influenza virus components [the influenza A (H3N2) strain] used to make this year’s vaccine has not grown as well as the corresponding strain used last year.

Secondly, the Food and Drug Administration (FDA) has taken regulatory action against two of the manufacturers licensed to distribute influenza vaccine in the U.S. Both manufacturers have indicated that they intend to make corrections to address the problems, but implementation of corrective actions will require time for completion.

What is being done to correct the situation?
Both manufacturers are working closely with FDA, but implementation of corrective actions will require time for both completion and review by FDA.

What does CDC recommend at this time in response to the expected delay in the availability of influenza vaccine and a possible vaccine shortage?
CDC and the Advisory Committee on Immunization Practices (ACIP) recommend that:

1. Implementation of organized influenza vaccination campaigns should be delayed.
   Health care providers, health organizations, commercial companies and other organizations planning organized, mass influenza vaccine campaigns for the 2000-2001 season should delay such programs until early to mid-November. The purpose of this recommendation is to minimize cancellations of vaccine campaigns and wastage of vaccine doses resulting from delays in vaccine delivery.
   
   Note: This recommendation does not apply to physicians who routinely administer or prescribe influenza vaccine for patients at high risk for complications of influenza.

2. Influenza vaccination of individuals at high risk for complications from influenza and their close contacts should proceed routinely during regular health care visits.
   Routine influenza vaccination activities in clinics, provider offices, hospitals, nursing homes and other health care settings, especially of high-risk individuals, health care staff and other persons in close contact with high-risk individuals, should proceed as normal with available vaccine.

3. Provider-specific contingency plans for an influenza vaccine shortage should be developed.
   All influenza vaccine providers, including health care systems and organizers of vaccination campaigns, should develop a provider-specific contingency plan to maximize vaccination of high-risk persons and health care workers. These plans should be available for implementation if a vaccine shortage develops.

What else is being emphasized for the 2000-01 season?
The other points that should be emphasized for this season are:

• Vaccine providers should continue to administer influenza vaccine to unvaccinated high-risk persons after mid-November and throughout the influenza season.
• Once vaccine is available, routine influenza vaccination of high-risk persons and their contacts should proceed normally, especially for high-risk young children who are receiving influenza vaccine for the first time and require two doses.
• Influenza vaccine purchasers should refrain from placing duplicate orders with multiple companies to minimize the amount of vaccine that is unused.
• In the context of a possible vaccine shortage, contingency plans for persons aged 50-64 years old should focus primarily on vaccinating individuals with high-risk conditions rather than the entire 50-64 year old age group.
• All health-care workers who have close contact with persons at high risk for complications from influenza should receive influenza vaccine.

Why did ACIP and CDC issue these adjunct recommendations at this time?
Many influenza vaccine providers must plan their fall vaccination activities now, even though the vaccine supply situation is unclear. Given the uncertainty about the influenza vaccine supply, implementation of the recommendations can help to increase vaccination of persons at high risk for complications from influenza.

Who is at high risk for complications from influenza?
In the U.S., 70 to 76 million people (approximately 35 million people aged > 65 years; 33 to 39 million people aged < 65 years with high-risk medical conditions; and 2 million pregnant women) are estimated to be at high risk for serious complications from influenza infections, including hospitalization or death. Persons at high risk for complications from influenza should receive annual vaccination and include the following:

• Persons aged 65 years and older;
• Residents of nursing homes and other chronic-care facilities with residents of any age who have chronic medical conditions;
• Adults and children aged 6 months and older who have chronic pulmonary or cardiovascular disease, including asthma;
• Adults and children aged 6 months and older who have required regular medical follow-up or hospitalization during the past year because of chronic metabolic diseases (including diabetes mellitus), kidney dysfunction, blood disorders (hemoglobinopathies), or immune system problems (immunocompromised e.g. HIV infection, immunosuppressed by medication, chemotherapy or radiation therapy);
• Children and teenagers (aged 6 months to 18 years) who are receiving long-term aspirin therapy and therefore might be at risk for developing Reye Syndrome afterinfluenza infection;
• Women who will be in the second or third trimester of pregnancy during the influenza season.

Note: Unvaccinated persons in all of the above groups should still be offered influenza vaccine even after influenza activity has been detected in a community as long as vaccine is available.

Who else should receive influenza vaccination each year?
Other persons who should be vaccinated each year include:

• Health-care workers, employees of hospitals, clinics, offices, and chronic care institutions who directly care for and have close contact with persons at high risk from complications of influenza.
• Household members (including children aged 6 months and older) of persons in high-risk groups (individuals who are most likely to transmit influenza to high-risk persons)

Note: Unvaccinated persons in all of the above groups should still be offered influenza vaccine even after influenza activity has been detected in a community as long as vaccine is available.

Have there been any problems producing influenza vaccine because of the selection of two new influenza virus strains this year?
Yes, some manufacturers have reported that the influenza A/Panama2007/99-like (H3N2) strain has not grown as well as the corresponding strain used last year.

When will influenza vaccine for the upcoming season be available?
Typically, influenza vaccine is usually first available for distribution in July. Most vaccine is usually available for administration by September or October. Limited quantities of influenza vaccine for the 2000-2001 influenza season will be released for distribution beginning in July. However, it is likely that less influenza vaccine than usual will be available at an early time this year and that there will be delays in availability.

How are the virus strains for influenza vaccine selected?
Influenza vaccine contains three different inactivated (killed) influenza virus strains. Since influenza viruses are continuously changing, the vaccine virus strains must be updated each year. The World Health Organization (WHO) makes recommendations for the composition of the influenza vaccines for the upcoming influenza seasons for the Northern and Southern Hemispheres. Each January through March, the U.S. Public Health Service (USPHS) by way of the Vaccine and Related Biological Products Advisory Committee at FDA (VRBPAC) begins the selection of influenza virus strains that will be included in the U.S. influenza vaccine for the upcoming fall. CDC, FDA, the National Institutes of Health (NIH) and others provide information on influenza vaccines and influenza viruses circulating in the U.S. and worldwide to assist WHO and USPHS in their decisions. Typically, the first strain recommendation is made by the USPHS in January and the process is completed by March. Each year, two influenza type A virus strains and one type B virus strain are chosen for inclusion in the vaccine.

Two new influenza type A virus strains [A/Panama/2007/99-like (H3N2) and A/New Caledonia/20/99-like (H1N1)] were recommended for inclusion in the 2000-2001 influenza vaccine. The third strain, B/Yamanashi/166/98-like virus, is unchanged from last year’s influenza vaccine. Occasionally, production of vaccine containing a new influenza virus strain may be affected by lower growth of vaccine viruses or unexpected processing problems. The introduction of new vaccine strains has had effects on vaccine production in the past. Different manufacturers may be affected differently, since manufacturing processes differ.

When should influenza vaccine be offered?
The optimal time for influenza vaccination is October through mid-November. To avoid missed opportunities for vaccination, persons at high risk for complications who are seen for routine care or are hospitalized should be offered influenza vaccine beginning in September, if vaccine is available. Unvaccinated persons at high risk for complications from influenza and residents of chronic care facilities should be offered influenza vaccine even after influenza activity has occurred in a community. Therefore, these groups should continue to be offered vaccine after mid-November and throughout the influenza season as long as vaccine is still available. In addition, health-care workers, employees of hospitals, clinics, offices, and chronic care institutions who directly care for and have close contact with persons at high risk from complications of influenza, and household members (including children aged 6 months and older) of persons in high-risk groups (individuals who are most likely to transmit influenza to high risk persons) should continue to be offered influenza vaccine if vaccine is available.

What can hospitals, public health clinics, nursing homes, and other groups do now to prepare for the 2000-01 season?
Institutions, and organizations can develop contingency plans to maximize influenza vaccination of high-risk persons and health-care workers if a shortage develops. These groups can also begin to work together with health departments to develop local networks to help re-distribute unused influenza vaccine or direct persons desiring vaccination to providers with available vaccine.

Does this mean that companies organizing large vaccination campaigns for their employees should cancel their programs for the upcoming season?
It is recommended that groups organizing mass vaccination campaigns should delay scheduling planned clinics until early to mid-November. The ultimate decision of whether to hold such organized campaigns or to modify them so that influenza vaccine is focused upon workers with high-risk conditions should depend upon further information about influenza vaccine availability. CDC and FDA will provide updates on the influenza vaccine supply situation as new information becomes available.

What impact could a potential shortage have on public health?
The public health impact will depend upon several factors. The main factors are the extent of the potential vaccine shortage and the severity of the upcoming influenza season. It is important to realize that the severity of the upcoming winter flu season is unknown and cannot be predicted. The severity of the season largely will be influenced by:

• How many people become infected,
• The specific influenza virus strains that predominate during the 2000-2001 season, and
• How many people are protected from infection and complications of influenza, especially high-risk persons.

Is this potential vaccine shortage related to the new recommendation that all persons aged 50 years and older should receive annual influenza vaccination?
Any increase in demand resulting from this new recommendation could increase the magnitude of a shortage. (Recently, the ACIP broadened its recommendations to include all persons between 50 and 64 years of age to be vaccinated each year. This recommendation was intended to increase vaccination levels of persons aged 50-64 years with high-risk conditions.) In the context of a possible vaccine shortage, it would be appropriate for contingency plans covering this age group to focus primarily on vaccinating persons with high-risk conditions rather than this entire age group.

How does the current vaccine situation affect recommendations for travelers?
There are no changes in the recommendations for travelers. Persons 50 years or older and younger individuals at high risk for complications of influenza who were not vaccinated last fall should contact their physicians to see if influenza vaccine is available, to discuss the signs, symptoms, and risk of influenza during their travels, and to discuss the advisability of carrying antiviral medications for influenza. The 1999-2000 influenza vaccine has expired for use. Availability of the 2000-2001 influenza vaccine is likely to be very limited until the late summer.

What about the new antiviral drugs for influenza? Will they help prevent me from getting the flu next winter?
The best way to prevent influenza virus infection is to receive influenza vaccine. Antiviral medications are not a substitute for influenza vaccination. Among the four medications approved by FDA for use in the U.S., the approved usages (treatment or chemoprophylaxis), age groups, dosages, routes of administration, routes of metabolism, adverse reactions, and costs vary and all of them require prescription by a physician.

Four antiviral drugs (amantadine, rimantadine, zanamivir, and oseltamivir) are approved by FDA for treatment of acute, uncomplicated influenza.

• Amantadine and rimantadine are active against influenza A viruses.
• Zanamivir and oseltamivir are active against influenza A and influenza B viruses. When used for treatment, these drugs are only effective if treatment is started within two days of the beginning of symptoms. All four antiviral agents can reduce the duration of influenza symptoms by about one day if treatment is started within 48 hours of symptom onset.
• Two antiviral drugs (amantadine and rimantadine) are approved by FDA for use as chemoprophylaxis (prevention) against influenza A. The use of these drugs has been associated with adverse reactions that affect the central nervous system and other side effects. Amantadine and rimantadine are not generally recommended for widespread use in healthy persons. The new antiviral drugs for influenza (zanamivir and oseltamivir) are not approved for prophylaxis of influenza.

Use of antiviral medications for the prevention of influenza can be highly effective in specific individuals or in certain situations such as for the control of influenza outbreaks in nursing homes. However, widespread routine use of antiviral drugs for chemoprophylaxis against influenza is an untested and expensive strategy that could result in large numbers of people experiencing adverse effects.

*Modified and adapted from "Prevention and Control of Influenza: Recommendations of the Advisory Committee on Immunization Practices (ACIP)" MMWR Recommendations and Reports, April 14, 2000 / 49(RR03);1-38. This report is available on-line at: ftp://ftp.cdc.gov/pub/Publications/mmwr/rr/rr4903.pdf

Further information about influenza is available at: http://www.cdc.gov/ncidod/diseases/flu/fluvirus.htm