Annual vaccination against influenza is the primary means for minimizing
serious adverse outcomes from influenza virus infections. These infections result
in approximately 20,000 deaths and 110,000 hospitalizations per year in the United
States (1). The amount of trivalent inactivated influenza vaccine produced for distribution
in the United States has increased substantially; in 1999, four manufacturers produced
a combined total of 80 to 85 million doses.
For the 2000--01 influenza season in the United States, lower than
anticipated production yields for this year's influenza A(H3N2) vaccine component and
other manufacturing problems are expected to lead to a substantial delay in the
distribution of influenza vaccine and possibly substantially fewer total doses of vaccine
for distribution than last year. A more precise estimate of the vaccine supply will
be available as production progresses during the summer. Because many
vaccine providers currently are planning their fall vaccination activities, CDC and the
Advisory Committee on Immunization Practices (ACIP) are issuing adjunct influenza
vaccination recommendations beyond those made by ACIP on April 14, 2000
(1). The adjunct recommendations are specific to the 2000--01 influenza season.
Adjunct Influenza Vaccine Use Recommendations for the 2000--01 Influenza Season
Implementation of organized influenza vaccination campaigns should be
delayed. Health-care providers, health organizations, commercial companies, and
other organizations planning organized influenza vaccination campaigns for the
2000--01 influenza season should delay vaccination campaigns 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.
Influenza vaccination of persons 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, offices, hospitals, nursing
homes, and other health-care settings (especially vaccination of persons at high risk
for complications from influenza, health-care staff, and other persons in close
contact with persons at high risk for complications from influenza) should proceed
as normal with available vaccine.
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.
Use of Influenza Antiviral Medications
There are no new recommendations for the use of influenza antiviral drugs.
The approved usage (i.e., for treatment or chemoprophylaxis), age group, dosage, route
of administration, metabolism, and adverse reactions of these agents vary
(1), and all of them require prescription by a physician. Influenza antiviral drugs are useful
for controlling influenza outbreaks in specific and circumscribed situations, such
as nursing homes. In addition, long-term antiviral chemoprophylaxis of
high-risk institutionalized residents or some persons at high risk for complications
from influenza might be indicated if vaccine either is unavailable, ineffective (e.g.,
severely immunocompromised persons), or contraindicated.
However, these drugs are not a substitute for influenza vaccine. Even if an
influenza vaccine shortage develops, CDC and ACIP do not support their routine and
widespread use as chemoprophylaxis against influenza because this is an untested and
expensive strategy that could result in large numbers of persons experiencing adverse effects.
Additional Discussion
In the United States, 70 to 76 million persons (approximately 35 million
persons aged >65 years; 33 to 39 million persons aged <65 years with high-risk
medical conditions; and 2 million pregnant women) are at high risk for serious
complications from influenza infections, including hospitalizations and deaths. The expected delay
in influenza vaccine distribution and a possible shortage for the 2000--01
influenza season has raised difficult questions of how to maximize protection against
influenza for these persons. One complicating factor is that many vaccine providers must
plan
their fall vaccination activities now even though the vaccine supply is uncertain.
Given the current situation, CDC and ACIP have issued modified recommendations for
the 2000--01 season emphasizing the delay of organized influenza vaccine campaigns
until November, the continuation of routine vaccination activities during regular
health-care visits, and the development of provider-specific contingency plans in case a
vaccine shortage should develop. There are additional important points worth emphasizing
in addition to these main recommendations:
Influenza vaccine administered after mid-November can still
provide substantial protective benefits. In general, ACIP recommends that
routine vaccination of persons at high risk for complications from influenza begin
in September. In previous years, ACIP has recommended that
organized campaigns take place during October through mid-November. These
timing recommendations balance several considerations, including the desirability
of administering vaccine before substantial seasonal influenza activity has
begun but not vaccinating so early such that vaccine antibody titers
might substantially decrease in some persons. Nonetheless, many persons
who should receive influenza vaccine remain unvaccinated after
mid-November, and for many of these persons, influenza vaccination after mid-November
will be beneficial. For the 2000--01 season, it is particularly important for
vaccine providers to continue to administer vaccine after mid-November.
Once vaccine is available, health-care workers should provide vaccine
to persons at high risk for complications from influenza as is normally done.
This is particularly important for young children at high risk who are
receiving influenza vaccination for the first time and who require two doses of vaccine.
Minimizing wastage of influenza vaccine is important. In particular,
influenza vaccine purchasers should refrain from placing duplicate orders with
multiple companies to minimize the amount of vaccine that is returned to
a manufacturer and discarded. Options to promote redistribution of vaccine
that otherwise would be returned or discarded are being developed.
In 2000, ACIP broadened its influenza vaccine recommendations to include
all persons aged 50--64 years. This recommendation was based, in part, on
an effort to increase vaccination coverage of persons in this age group 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.
Influenza vaccine is routinely recommended for persons in close contact
with persons at high risk for complications from influenza because such
persons are in a position to transmit influenza virus infection to high-risk
persons. Vaccination of health-care workers has been highlighted in particular
because health-care workers have frequent and close contact with many different
high-risk persons at a time when high-risk persons are particularly vulnerable.
As new information becomes available, CDC and the Food and Drug
Administration (FDA) will issue updates. In the meantime, ACIP and CDC request that persons
and organizations planning to administer influenza vaccine, as well as members of
the general public, join in these efforts to maximize protection of persons most likely
to develop serious and life-threatening complications from influenza. FDA, CDC,
ACIP,
National Institutes of Health, and vaccine manufacturers will continue to work
together to facilitate the availability of influenza vaccine for the upcoming season and
to minimize the adverse impact of an influenza vaccine shortage if one should develop.
If a substantial vaccine shortage appears imminent, or if the situation warrants,
then CDC and ACIP will issue further recommendations.
Reference
CDC. Prevention and control of influenza: recommendations of the Advisory Committee
on Immunization Practices (ACIP). MMWR 2000;49(no. RR-3).
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