04-29-2009, 05:11 AM
<!--QuoteBegin-ramana+Apr 29 2009, 01:16 AM-->QUOTE(ramana @ Apr 29 2009, 01:16 AM)<!--QuoteEBegin-->Question since immunization is based on old dead virus, and if this is new virus who does the old dead virus based Tamiflu help immunize the population?
Is it a palliative or placebo?
[right][snapback]96755[/snapback][/right]
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Tamiflu (Oseltamivir) will just reduce duration of symptoms (of regular influenza infection) by 1 to 1.5 days. It does not vaccinate against the virus. It can be given as chemoprophylaxis, effectiveness is 84%.
<!--QuoteBegin-->QUOTE<!--QuoteEBegin-->Prophylaxis
Inactivated and live attenuated vaccines against influenza are available, and their use represents the major public health measure for prevention of influenza. The vast majority of currently used vaccines are inactivated ("killed") preparations derived from influenza A and B viruses that circulated during the previous influenza season. If the vaccine virus and the currently circulating viruses are closely related, 50-80% protection against influenza would be expected from inactivated vaccines. The available inactivated vaccines have been highly purified and are associated with few reactions. Up to 5% of individuals experience low-grade fever and mild systemic symptoms 8-24 h after vaccination, and up to one-third develop mild redness or tenderness at the vaccination site. Since the vaccine is produced in eggs, individuals with true hypersensitivity to egg products either should be desensitized or should not be vaccinated. Although the 1976 swine influenza vaccine appears to have been associated with an increased frequency of Guillain-Barre syndrome, influenza vaccines administered since 1976 generally have not been. Possible exceptions were noted during the 1992-1993 and 1993-1994 influenza seasons, when there may have been an excess risk of Guillain-Barre syndrome of slightly more than 1 case per million vaccine recipients. However, the overall health risk following influenza outweighs the potential risk associated with vaccination.
The U.S. Public Health Service recommends the administration of inactivated influenza vaccine to individuals who, because of age or underlying disease, are at increased risk for complications of influenza and to the contacts of these individuals (Table 180-3). Inactivated vaccines may be administered safely to immunocompromised patients. Influenza vaccination is not associated with exacerbations of chronic nervous-system diseases such as multiple sclerosis. Vaccine should be administered early in the autumn before influenza outbreaks occur and should then be given annually to maintain immunity against the most current influenza virus strains.
[TABLE 180-3. Persons for Whom Annual Influenza Vaccination Is Recommended]
A live attenuated influenza vaccine that is administered by intranasal spray is also available. The vaccine is generated by reassortment between currently circulating strains of influenza A and B virus and a cold-adapted, attenuated master strain. The cold-adapted vaccine is well tolerated and highly efficacious (92% protective) in young children; in one study, it provided protection against a circulating influenza virus that had drifted antigenically away from the vaccine strain. Live attenuated vaccine is approved for use in healthy persons 5-49 years of age.
Antiviral drugs may also be used as chemoprophylaxis against influenza (Table 180-2).<b> Chemoprophylaxis with oseltamivir (75 mg/d by mouth) or zanamivir (10 mg/d inhaled) has been 84-89% efficacious against influenza A and B. </b>Chemoprophylaxis with amantadine or rimantadine is no longer recommended because of reports of widespread resistance to these drugs. In earlier studies with sensitive viruses, prophylaxis with amantadine or rimantadine (100-200 mg/d) was 70-100% effective against illness associated with influenza A. Chemoprophylaxis is most likely to be used for high-risk individuals who have not received influenza vaccine or in a situation where the vaccines previously administered are relatively ineffective because of antigenic changes in the circulating virus. During an outbreak, antiviral chemoprophylaxis can be administered simultaneously with inactivated vaccine, since the drugs do not interfere with an immune response to the vaccine. In fact, there is evidence that the protective effects of chemoprophylaxis and inactivated vaccine may be additive. However, concurrent administration of chemoprophylaxis and the live attenuated vaccine may interfere with the immune response to the latter. Antiviral drugs should not be administered until at least 2 weeks after administration of live vaccine, and vaccination with live vaccine should not begin until at least 48 h after antiviral drug administration has been stopped. Chemoprophylaxis may also be employed to control nosocomial outbreaks of influenza. For that purpose, prophylaxis should be instituted promptly when influenza activity is detected and must be continued daily for the duration of the outbreak.<!--QuoteEnd--><!--QuoteEEnd-->
Is it a palliative or placebo?
[right][snapback]96755[/snapback][/right]
<!--QuoteEnd--><!--QuoteEEnd-->
Tamiflu (Oseltamivir) will just reduce duration of symptoms (of regular influenza infection) by 1 to 1.5 days. It does not vaccinate against the virus. It can be given as chemoprophylaxis, effectiveness is 84%.
<!--QuoteBegin-->QUOTE<!--QuoteEBegin-->Prophylaxis
Inactivated and live attenuated vaccines against influenza are available, and their use represents the major public health measure for prevention of influenza. The vast majority of currently used vaccines are inactivated ("killed") preparations derived from influenza A and B viruses that circulated during the previous influenza season. If the vaccine virus and the currently circulating viruses are closely related, 50-80% protection against influenza would be expected from inactivated vaccines. The available inactivated vaccines have been highly purified and are associated with few reactions. Up to 5% of individuals experience low-grade fever and mild systemic symptoms 8-24 h after vaccination, and up to one-third develop mild redness or tenderness at the vaccination site. Since the vaccine is produced in eggs, individuals with true hypersensitivity to egg products either should be desensitized or should not be vaccinated. Although the 1976 swine influenza vaccine appears to have been associated with an increased frequency of Guillain-Barre syndrome, influenza vaccines administered since 1976 generally have not been. Possible exceptions were noted during the 1992-1993 and 1993-1994 influenza seasons, when there may have been an excess risk of Guillain-Barre syndrome of slightly more than 1 case per million vaccine recipients. However, the overall health risk following influenza outweighs the potential risk associated with vaccination.
The U.S. Public Health Service recommends the administration of inactivated influenza vaccine to individuals who, because of age or underlying disease, are at increased risk for complications of influenza and to the contacts of these individuals (Table 180-3). Inactivated vaccines may be administered safely to immunocompromised patients. Influenza vaccination is not associated with exacerbations of chronic nervous-system diseases such as multiple sclerosis. Vaccine should be administered early in the autumn before influenza outbreaks occur and should then be given annually to maintain immunity against the most current influenza virus strains.
[TABLE 180-3. Persons for Whom Annual Influenza Vaccination Is Recommended]
A live attenuated influenza vaccine that is administered by intranasal spray is also available. The vaccine is generated by reassortment between currently circulating strains of influenza A and B virus and a cold-adapted, attenuated master strain. The cold-adapted vaccine is well tolerated and highly efficacious (92% protective) in young children; in one study, it provided protection against a circulating influenza virus that had drifted antigenically away from the vaccine strain. Live attenuated vaccine is approved for use in healthy persons 5-49 years of age.
Antiviral drugs may also be used as chemoprophylaxis against influenza (Table 180-2).<b> Chemoprophylaxis with oseltamivir (75 mg/d by mouth) or zanamivir (10 mg/d inhaled) has been 84-89% efficacious against influenza A and B. </b>Chemoprophylaxis with amantadine or rimantadine is no longer recommended because of reports of widespread resistance to these drugs. In earlier studies with sensitive viruses, prophylaxis with amantadine or rimantadine (100-200 mg/d) was 70-100% effective against illness associated with influenza A. Chemoprophylaxis is most likely to be used for high-risk individuals who have not received influenza vaccine or in a situation where the vaccines previously administered are relatively ineffective because of antigenic changes in the circulating virus. During an outbreak, antiviral chemoprophylaxis can be administered simultaneously with inactivated vaccine, since the drugs do not interfere with an immune response to the vaccine. In fact, there is evidence that the protective effects of chemoprophylaxis and inactivated vaccine may be additive. However, concurrent administration of chemoprophylaxis and the live attenuated vaccine may interfere with the immune response to the latter. Antiviral drugs should not be administered until at least 2 weeks after administration of live vaccine, and vaccination with live vaccine should not begin until at least 48 h after antiviral drug administration has been stopped. Chemoprophylaxis may also be employed to control nosocomial outbreaks of influenza. For that purpose, prophylaxis should be instituted promptly when influenza activity is detected and must be continued daily for the duration of the outbreak.<!--QuoteEnd--><!--QuoteEEnd-->