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[medboy]

Is there a vaccine against pandemic influenza?

    If a new pandemic virus strain emerges, there will be a focused effort by public health authorities and manufacturers worldwide to develop, distribute, and administer an effective and specific pandemic vaccine. However, the process is complicated and will take a number of months before a vaccine would be available. Currently, vaccine against the influenza virus A/H5N1 is being developed and tested but the vaccine is not yet available for general or widespread use. Moreover, the current vaccine containing a recent H5N1 virus may or may not be effective against a future H5N1 strain, if such a strain emerges with the ability to spread easily among people.

    WHO will closely follow the development, protective effect, and safety of both the A/H5N1 and any other new pandemic vaccine and will make recommendations on its use as soon as the product is available. If deemed appropriate based on safety and efficacy, WHO will also contact manufacturers in advance to determine arrangements to procure vaccine in advance of its need. Under the best of circumstances, given the global population size and limited production capacity for influenza vaccine, any pandemic vaccine will initially be in short supply. Demand will far outstrip availability.

What is the difference between Tamiflu and the flu vaccine?

    Tamiflu is a drug used to treat a patient already ill with influenza while the vaccine is taken in advance to prevent contamination with the influenza virus.

Is it necessary/recommended to get the flu vaccine?

    The existing flu vaccine protects only against seasonal influenza and would probably give no protection at all against avian flu. It is, however, recommended for everyone to get this seasonal flu vaccine to avoid a possible dual infection with seasonal flu and avian flu in the same patient that might increase the risk of viral genetic reassortment. Having the vaccine against the seasonal flu would offer not only protection but also save a person from trouble when traveling. If a person is ill with seasonal flu (not with avian flu) after the onset of the avian flu pandemic, the patient will surely have trouble with airport authorities when traveling and might be placed in isolation/quarantine. This scenario can be avoided if the traveler is already vaccinated against the seasonal flu vaccine.

    A specific human vaccine for the H5N1 flu is presently under research and might be available within the next few months. However, its effectiveness cannot be assured as long as the new strain that might cause the next pandemic has not emerged yet.

Why do we need to get vaccinated against seasonal influenza?

    There is a vaccine available each year to protect against seasonal human influenza. All ADB personnel and their dependents, particularly those at high risk for developing serious medical complications from influenza, are encouraged to take advantage of this protective measure. This vaccine can provide protection against seasonal influenza which can be very serious for many individuals. Influenza vaccine can also be a highly cost-effective countermeasure against seasonal influenza.

    While seasonal influenza vaccine will not protect against a pandemic strain and does not provide protection against many other viruses that can cause respiratory illnesses, widespread use of seasonal influenza vaccines may be very helpful for a pandemic situation. Any reduction in seasonal influenza cases due to use of seasonal influenza vaccine will reduce the possibility that a case of seasonal influenza might be mistaken for a case of pandemic influenza, thereby reducing unnecessary worry and actions.

How effective are antiviral medications in combating avian influenza?

    In recent years, new antiviral agents to prevent or treat influenza infections have been developed. Two classes of drugs are available (the M2 inhibitors such as amantadine and rimantadine and the neuraminidase inhibitors such as oseltamivir and zanimivir). These drugs have been licensed for the prevention and treatment of human seasonal influenza in some countries.

    However, initial analysis of viruses isolated from the recent human cases of A/H5N1 indicates that many of these viruses currently are resistant to the M2 inhibitors. In addition, only the neuraminidase inhibitors have been shown, in animal laboratory tests, to be effective against influenza virus A/H5N1. At this time, there is extremely little real world clinical experience with use or effectiveness of antiviral drugs against H5N1 viral infections in humans. Among the neuramindase inhibitors, the only drug easily deliverable (orally in capsules) is oseltamivir, known in its only commercial form as Tamiflu®).

    Other antivirals, such as amantadine, have not shown effectiveness against A/H5/N1 in laboratory settings, but could potentially have some effectiveness against another new emerging strain.

I have heard that obtaining a “pneumococcal vaccination" is also required. Is this true?

    Pneumococcal vaccine should be considered for people at particular risk for the bacterial pneumonia complication of influenza. These include persons 65 years of age or older; those with heart failure, emphysema, diabetes mellitus, alcoholism, or chronic liver disease; and those who are otherwise immune compromised. The UN Medical Services recommend procuring pneumococcal vaccines for 10% of staff, and ADB will be following this advice.

Who will be the priority recipients for a vaccination when it is available?

    Prioirity recipients will include those involved with direct clinical contact with patients, those staff required to maintain essential functions, and those at particularly high risk of serious complications, such as the elderly and those with chronic diseases. Such priority lists, as developed, will have to be compatible with recommendations made for the international community at the time the vaccine becomes available. ADB Medical Services will follow WHO recommendations. However, it is also anticipated that more detailed priority lists may be developed at national and local levels that, inevitably, will reflect some differences in terms of local preferences.

What guidance can be offered on the use of oseltamivir (Tamiflu) as prophylaxis or treatment?

    Prophylaxis (Pre-Exposure)
    Antiviral drugs used for prophylaxis are given to people who are not infected and who are not ill. The purpose of prophylaxis is to try and prevent the development of severe pandemic disease in people who are potentially exposed to pandemic influenza.

    Oseltamivir (Tamiflu) can be offered to selected staff members who are needed by an organization to maintain its essential functions. The current prophylactic regimen is one tablet of 75 milligram (mg) per day. The upper limits for safe use of oseltamivir (Tamiflu) as prophylaxis are unknown. However, it is assumed that based on past pandemics and epidemics that in local areas, the duration of elevated risk of exposure to the pandemic virus in an area will be several weeks. In ADB's Pandemic Management Plan, to aid planning efforts, this period has been defined as 6 weeks. Use of antiviral drugs for prophylaxis is extremely resource consuming. Therefore, pre-exposure prophylaxis should be limited to maintenance of essential functions of an organization. Since pandemic influenza is an infection transmitted primarily by respiratory droplets, during a pandemic, the risk of infection will be relatively similar for most people in ADB except persons such as medical workers, who will be at highest risk because of their frequent contact with many ill persons.

    As an alternative to daily prophylaxis, antiviral drugs could be reserved for treatment of persons if fever or other symptoms of infection develop. This approach could stretch the supply of available antiviral drugs, but also is more complicated logistically to implement and might be less effective theoretically in preserving maintenance of essential functions.

    Treatment
    (i) Of ill persons: In symptomatic patients suspected of having pandemic influenza, oseltamivir (Tamiflu) can be administered as treatment. Current recommendations for treatment, based on treatment against seasonal influenza, are is two 75 mg capsules a day (total of 150 mg per day) for 5 days. There are no data for use for children below the age of 1 year. Oral suspension for children could be administered up to 40 kilograms (kg) when adult dosage can be used (ref: product information). For maximum effect, the drug should be started within 48 hours of onset of symptoms. During a pandemic situation, the possibility to test an individual patient for influenza infection will be extremely limited and therefore decision about whether to treat or not will depend upon clinical findings. Moreover, current recommendations on the amount and duration of treatment may change as more information becomes available about the effectiveness of dosages of antiviral drugs against pandemic influenza.

    (ii) Post-exposure (prophylaxis) treatment: Theoretically if the local supply is considered adequate, then oseltamivir (Tamiflu) could be provided to a person who does not have symptoms but who has had close and unprotected contact with another person who is suspected or confirmed to have pandemic influenza. In this situation it will not be clear if the exposed person is infected. However, giving that person antiviral drug theoretically could potentially protect the person from infection or reduce the severity and duration of the disease if the person has become infected. The drug would be administered in treatment doses as detailed above. The effectiveness or efficiency of this approach in preventing illness is theoretical, however, and has not been demonstrated. Moreover, for most people it will not be known if they were "exposed" to pandemic influenza and during a widespread pandemic, it will not be feasible to give post-exposure treatment to most non-ill contacts. In most situations, it is expected that most oseltamivir will be used for treatment of persons with febrile or respiratory illnesses rather than prophylaxis.

Is the antiviral drug Relenza as effective as Tamiflu? Do you recommend its use?

    Relenza seems to be as effective as Tamiflu in treating influenza. However, its administration to a patient is more complicated than Tamiflu and it does not have great capacity of production. Available stocks of Relenza are presently much smaller than available stocks of Tamiflu.
Can I take pain relievers when I develop flu symptoms or will these just provide temporary relief and mask the real cause?

    You can take pain relievers when having a flu but that cannot be considered as a treatment of the disease since the pain relievers will not affect the development of the virus and the course of the disease. Symptoms of influenza include muscle pains and fever but also cough and sometimes difficulty in breathing that will not be treated with pain-killers; thus, pain-killers will hardly mask the symptoms of an infected patient.

credits: adb.org