By Susan Dolan, RN, MS, CIC
1. To define influenza and recognize its symptoms.
2. To distinguish between influenza viruses and identify their traits.
3. To employ strategies for the influenza vaccine and prevent the spread of influenza.
"The flu" represents different things to different people. The termis often used incorrectly to describe a cold or a diarrheal illness, which aremost likely due to other viruses such as rhinovirus or rotavirus. Moreaccurately, flu is short for influenza, a much more serious illness known toaffect 10 percent to 20 percent of the U.S. population each year. Annually, morethan 110,000 people are hospitalized and 20,000 succumb to the virus and itsassociated complications.
Influenza is characterized by sudden onset of fever, chills, headache, sorethroat, runny nose, non-productive cough, severe malaise, photophobia (lightsensitivity) and muscle aches. Secondary complications can include pneumonia,encephalopathy, myositis, myocarditis, pericarditis, Reye's syndrome,transeverse myelitis and death.
There are A, B and C influenza viruses. The A and B strains are responsiblefor the epidemics we experience each winter and are separated into groups basedon their antigenic characteristics. Influenza A viruses are further categorizedon the basis of two surface antigens called hemagglutinin (H) and neuraminidase(N). As the A and B viruses replicate, they can undergo mutations from antigenicchanges, which can result in a new variant of the virus. Components of thevaccine are often changed each year to account for this drift in virus makeup.The duration of protection from the vaccine is less than one year so it isnecessary to get vaccinated each year with the new vaccine.
Influenza C is not responsible for epidemics but may cause mild respiratorysymptoms or no symptoms at all. Humans are the only known reservoir for B and Cstrains, but A strains may infect humans and animals.
Influenza is spread from person to person by aerosolized or droplettransmission through coughing, sneezing and direct contact with the virus orcontaminated objects. The time from influenza exposure to the onset of symptomsis one to three days and a person with influenza can be contagious from the daybefore they have symptoms until one week later. Young children and those who areimmunocompromised can shed the virus longer.
The morbidity and mortality associated with influenza has prompted efforts toprevent the acquisition and spread of the disease. Vaccine campaigns areimplemented in an effort to protect individuals most at-risk for complicationsof influenza. The Centers for Disease Control (CDC) Advisory Committee onImmunization Practices (ACIP) provides annual recommendations for the preventionand control of influenza. The ACIP uses viral isolate information submitted byworldwide influenza surveillance labs to ascertain which viruses are incirculation. The information is used to determine the composition of the fluvaccine for the following influenza season.
Each year the vaccine contains two A strains and one B strain. The vaccinefor the 2002-2003 influenza season will include the following strains:A/Moscow/10/99 (H3N2)-like, A/New Caledonia/20/99 (H1N1)-like and B/HongKong/330/2001-like strains. The two A components are the same as those used inthe 2001-2002 season vaccine, but the B component will be different. The changein the B component for the 2002-2003 vaccine was recommended because of thetypes of influenza B viruses circulating throughout the world.
The past two flu seasons, some manufacturers were delayed in distributing thevaccine due in large part to difficulties encountered with growing properties ofone of the strains. It was frustrating when health clubs had vaccine toadminister while hospitals did not have enough for high-risk patients.
Shipments of flu vaccine did come in, but were delayed and came inincrements, forcing some to prioritize who could get the vaccine. In ourhospital, representatives from high-risk departments determined how many vialswould be needed and worked closely with pharmacy staff to identify how manyvials of vaccine could be given to each department when part of the vaccineorder arrived.
Many strategies are used in our hospital to maximize administration of theinfluenza vaccine.
Who should be vaccinated?
For the 2002-2003 influenza season, the ACIP encourages vaccinations forhealthy children from 6 months old to 23 months old and their household membersbecause of the increased risk for influenza-related hospitalizations in thisyoung population. An official recommendation is expected in a year or so. Thosein contact with children less than 6 months old should be vaccinated because thechildren are too young to receive the vaccine and are at the greatest risk ofhospitalization for influenza-related illnesses.
An influenza vaccine is recommended for:
What are the contraindications to receiving the influenza vaccination?
When should vaccinations programs be initiated?
For the 2002-2003 season, the ACIP recommends prioritizing vaccinationefforts in October to target healthcare providers and persons at high risk ofcomplications from influenza. Children 6 months old to 9 years old receiving theinfluenza vaccine for the first time should receive their initial dose inOctober and require a booster dose one month after the initial dose. Othersshould not begin vaccination until November. This was the strategy recommendedby the ACIP the previous two flu seasons due to the delay in vaccinedistribution.
What are the side effects of the vaccine?
Influenza vaccine contains only non-infectious (inactivated) virus; thereforeit cannot cause influenza. The most frequent side effect of vaccination reportedby less than one third of recipients is soreness at the vaccination site that upto two days. Fever, malaise, myalgia and other systemic symptoms occurinfrequently and most often affect persons who have not had prior exposure tothe influenza virus antigens in the vaccine. These reactions begin six to 12hours after the vaccination and may persist for one to two days. Symptomaticrelief may be obtained by using non-aspirin-containing analgesics. Aspirinshould not be used for children due to the association of Reye's syndrome withinfluenza.
Immediate (presumably allergic) reactions such as hives, angioedema, allergicasthma and systemic anaphylaxis occur rarely and probably result fromhypersensitivity to a vaccine component, a majority of which are most likelyrelated to residual egg protein in the vaccine.
Can influenza vaccine be administered with other vaccines?
Influenza and pneumococcal vaccines may be administered at the same timeusing different sites without increasing side effects. However, influenzavaccine must be administered each year whereas pneumococcal vaccine is not.Children may receive influenza vaccine at the same time they receive otherroutine vaccinations including pertussis vaccine.
Should patients be tested for influenza?
Various methods for lab detection of influenza exist. The more rapiddiagnostic tests can be useful in identifying influenza to initiate some of thenewer treatment regimens. Isolation of the virus in culture is helpful whendesignated labs provide these isolates to laboratories that perform strainidentification. This is helpful in knowing whether or not the vaccine iseffective against the strains of influenza currently circulating. Theidentification of influenza can offer an early picture of local flu patterns. Ingeneral, testing should not be performed unless the information will alter theplan of care for the patient.
What about influenza medications for treatment and prophylaxis?
While vaccination remains the primary method of preventing and controllinginfluenza, influenza medications should be part of the plan for preventinginfluenza. Medications are used to treat ill patients, personnel, for theprophylaxis of exposed patients, unvaccinated individuals and those vaccinatedless than two weeks before exposure.
Antiviral medications like amantadine and rimantadine work by interferingwith the replication cycle of Influenza A. They should be started as soon aspossible after the onset of symptoms to be effective and can be continued fortwo to seven days depending on clinical improvement. Both medications areapproved by the FDA for children and adults for prophylaxis against Influenza Ainfection. The guidelines for prophylaxis include high-risk persons who arevaccinated after the start of a community outbreak of Influenza A, healthcareproviders not vaccinated prior to the start of the outbreak, immune deficientpatients who may have inadequate response to vaccine and persons for whom thevaccine is contraindicated. Amantadine is the only currently approved antiviralfor the treatment of children with influenza. These medications are noteffective against influenza B infections.
In 1999, the FDA approved two new antivirals for the treatment of influenzain patients who have been symptomatic for no more that two days. Thesemedications inhibit the enzyme neuraminidase and inhibit viral penetration ofthe mucus lining, thereby inhibiting the release of the virus out of cells thatare already infected. Zanamivir and oseltamivir have been shown to decrease theduration of flu-related symptoms by one to one-and-a-half days. Oseltamivir,administered via an oral capsule, has been approved for prophylaxis in patientsolder than 13. Zanamivir, administered via oral inhalation, has been approvedfor the treatment of patents 7 years and older, while oseltamivir is approvedfor treatment of children older than 1 year.
The limitations of these medications are that they must be administeredwithin 48 hours of the onset of symptoms, have not been shown to prevent diseasetransmission and have not been adequately studied in patients with serioushealth conditions or with renal or hepatic impairments. Additionally,oseltamivir has shown some benefit as a prophylactic agent when given once dailyfor six weeks, although the cost may be prohibitive.
These medications are not without contraindications and precautions.Zanamivir is not recommended for patients with underlying airway diseaseincluding asthma or chronic obstructive pulmonary disease (COPD) because of thelack of safety and efficacy data in these patents. Serious adverse eventsincluding bronchospasm and decline in lung function have been reported withzanamivir use, most commonly in patients with underlying airway disease. Ifzanamivir is used in patients with underlying airway disease, they should beinstructed to have a fast-acting bronchodilator available.
What is the nasal spray vaccine all about?
The intranasal influenza vaccine is a live-attenuated, cold-adapted trivalent(three viruses) influenza vaccine administered intranasally. Cold-adapted meansthe virus has adapted to growing in colder temperatures. It can infect thecooler upper respiratory tract and stimulate immunity, but not cause disease inthe warmer lungs.
A five-year trial showed this vaccine to be as effective as the currentlyavailable inactivated vaccine. The nasal vaccine was studied during the1996-1997 flu season. In the study of 1,602 children, 1 percent of thosereceiving the nasal vaccine and 18 percent of the placebo group developedinfluenza. The nasal vaccine is 93 percent effective in preventing disease.There were 30 percent fewer episodes of otitis media in vaccine recipientscompared to controls. FDA approval is still pending with hope that the vaccinemay be available this coming season, although there will be cost considerations.
Susan Dolan, RN, MS, CIC, is hospital epidemiologist for The Children'sHospital, Denver, and Educator of the Year, Infection Control Today magazine.