Epidemics of influenza occur during the winter months nearly every year. Influenza vaccine is the primary method for preventing influenza and minimizing serious adverse outcomes from influenza virus infections. For the upcoming 2000-2001 season, there have been some changes to previous recommendations and some important developments regarding vaccine availability. This report summarizes recommendations of the Advisory Committee on Immunization Practices (ACIP) for the use of influenza vaccine and antiviral agents for the 2000-2001 influenza season. Complete copies of the guidelines are available through the Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report, Prevention and Control of Influenza, Recommendations of the Advisory Committee on Immunization Practices (ACIP) April 14, 2000/Vol. 49 {No. RR-3} and Notice to Readers: Delayed supply of influenza Vaccine and Adjunct ACIP Influenza Vaccine Recommendations for the 2000-01 Influenza Season, July 14, 2000/Vol.49(27);619-622.

The trivalent influenza vaccine prepared for the 2000-2001 season will include A/Moscow/10/99 (H3N2)-like, A/New Caledonia/20/99 (H1N1)-like, and B/Beijing/184/93-like antigens. Because the vaccine viruses are initially grown in embryonated hens’ eggs, the vaccine might contain small amounts of residual egg protein. Influenza vaccine distributed in the United States might also contain thimerosal, a mercury-containing compound, as the preservative.

Vaccination is recommended for the following groups of persons who are at increased risk for complications from influenza or who have a higher prevalence of chronic medical conditions that place them at risk for influenza-related complications:

• persons aged >50 years (previously recommended for ages >65 years)

• residents of long-term care centers

• adults and children who have chronic disorders of the pulmonary or cardiovascular systems, including asthma

• adults and children who have required regular medical follow-up or hospitalization during the preceding year because of chronic metabolic diseases (including diabetes mellitus), renal dysfunction, hemoglobinopathies, or immunosuppression (including immunosuppression caused by medications or by human immunodeficiency virus)

• 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 after influenza infection

• women who will be in the second or third trimester of pregnancy during the influenza season.

Vaccination of healthcare workers and others in close contact with persons at high risk for complications from influenza is also recommended. These groups include:

• physicians, nurses, and other personnel in both hospital and outpatient-care settings including emergency response workers

• employees of long-term care centers who have contact with patients or residents

• employees of assisted living and other residences for persons in high-risk groups

• persons who provide home care to persons in high-risk groups

• household members (including children) of persons in high-risk groups

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. This raises some difficult questions of how to maximize protection against influenza. One complicating factor is that many vaccine providers must plan their fall vaccination activities now even though the vaccine supply is uncertain. A more precise estimate of the vaccine supply will be available as production progresses. In the meantime, CDC and ACIP have made the following recommendations:

• Implementation of organized influenza vaccination campaigns should be delayed until early to mid-November. Influenza vaccine administered after mid-November can still provide substantial protective benefits. The purpose of this recommendation is to minimize cancellations of vaccine campaigns and wastage of vaccine doses resulting from delays in vaccine delivery.

• Also to minimize wastage, influenza vaccine purchasers should refrain from placing duplicate orders with multiple companies to minimize the amount of vaccine that otherwise would be returned to a manufacturer and discarded. Options to promote redistribution of vaccine that otherwise would be returned or discarded are being developed by CDC.

• Influenza vaccination of persons at high risk for complications from influenza and their close contacts should proceed routinely during regular healthcare visits. Routine influenza vaccination activities in clinics, offices, hospitals, nursing homes, and other healthcare settings should proceed as normal with available vaccine. This is particularly important for children at high risk who are receiving influenza vaccination for the first time and who require two doses of vaccine.

• 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 healthcare workers. These plans should be available for implementation if a vaccine shortage develops.

• ACIP broadened it’s 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. However, in the context of a possible vaccine shortage, it would be appropriate to focus primarily on vaccinating persons with high-risk conditions rather than this entire age group.

ACIP and CDC have requested 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. If a substantial vaccine shortage appears imminent, or if the situation warrants, further recommendations will be issued.

Antiviral drugs for influenza are an important adjunct to influenza vaccine for the control and prevention of influenza. However, they are not a substitute for vaccination. 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. Four currently licensed agents are available in the United States: amantadine, rimantadine, zanamivir, and oseltamivir. All require a prescription by a physician. The approved usage (i.e., for treatment or chemoprophylaxis), age group dosage, route of administration, metabolism, and adverse reactions of these agents vary. (See table 1)

Laboratory Diagnosis and Disease Surveillance

The appropriate treatment of patients with respiratory illness depends on accurate and timely diagnosis. The early diagnosis of influenza can help reduce the inappropriate use of antibiotics and provide the option of using antiviral therapy. Several commercial rapid diagnostic tests are available that can be used by laboratories in outpatient settings to detect influenza viruses within 30 minutes. Some of these rapid tests detect only influenza A viruses, whereas other rapid tests detect both influenza A and B viruses but do not distinguish between the two types.

Despite the availability of rapid diagnostic tests, the collection of clinical specimens for viral culture is important because only culture isolates can provide specific information on circulating influenza subtypes and strains. This information is needed to compare current circulating influenza strains with vaccine strains, to guide decisions about influenza treatment and prophylaxis, and to formulate vaccine for the coming year. Virus isolates also are needed to monitor the emergence of antiviral resistance. Healthcare providers in Utah are encouraged to submit clinical specimens to the Utah Public Health Laboratory for virus isolation and typing. Nasopharangeal aspirates, nasal swabs and nasal washes obtained within three days of clinical onset are suitable clinical specimens. For some rapid testing methods the media used to store the specimen is inappropriate for viral culture; in this case, it is necessary to collect two separate samples.

Because influenza viruses undergo constant antigenic change, both virologic surveillance and disease surveillance are necessary to identify influenza virus variants and to determine their ability to spread and cause disease. Lab confirmed influenza is reportable in Utah per the Communicable Disease Rule R386-702. Also, each influenza season, the Bureau of Epidemiology participates in CDC’s sentinel physician surveillance system. Each week from October through May, staff from the Communicable Disease Control Program will contact select physicians who report the number of patient visits for the week and the number of those patients examined for influenza-like illness. Also, school absenteeism rates are calculated based on reports from selected schools and school districts. This information is used to estimate the level of influenza activity in the state. Activity is categorized and reported to CDC as “no activity”, “sporadic”, “regional”, or “widespread”. “Sporadic” activity is defined as sporadically occurring cases of influenza-like illness or culture-confirmed influenza with no outbreaks detected. “Regional” activity is outbreaks of influenza-like illness or culture-confirmed influenza occurring in counties in which the combined population is <50% of the total state population. “Widespread” activity is outbreaks of influenza-like illness or culture-confirmed influenza in counties with a combined population of $50% of the total state population. Utah surveillance data is updated weekly on the Bureau of Epidemiology website (www.health.state.ut.us/els). Here you will also find links to the CDC influenza website for national influenza surveillance data. Sentinel physicians and schools are currently being recruited for participation in the 2000-01 surveillance season. If you are interested in participating or if you have questions, please contact the Bureau of Epidemiology at (801)538-6191.

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The Epidemiology Newsletter is published monthly by the Utah Department of Health, Division of Epidemiology and Laboratory Services, Bureau of Epidemiology, to disseminate epidemiologic information to the health care professional and the general public.

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