The last report of CDC, about the effectiveness of the influenza vaccine during this flu season from January 16 reported that the influenza vaccine for the 2014/2015 flu season has efficiency only 23% for all age groups.
One factor that determines how well a flu vaccine works is the similarity between the flu viruses used in vaccine production and the flu viruses actually circulating. During seasons when vaccine viruses and circulating influenza viruses are well matched, vaccine effectiveness between 50 percent and 60 percent has been observed.
H3N2 viruses have been predominant so far this season, but about 70 percent of them have been different or have “drifted” from the H3N2 vaccine virus. This likely accounts for the reduced vaccine effectiveness.
MMWR report highlights the need for additional funds for treatment and prevention of influenza, due to reduced effectiveness of the flu vaccine, including the use of appropriate and influenza antiviral medications.
Influenza antiviral drugs are effective in the relief of flu symptoms and the prevention of complications. They are an important tool in reducing the severity of influenza. Unfortunately one recent study reported that only 19% of high-risk patients who could benefit from treatment with influenza antiviral medications are done. Last flu season influenza antiviral drugs have been underused.
Influenza antiviral drugs are most effective if you start to take in the first 48 hours of the onset of flu symptoms. According to a limited study of CDC many doctors do not prescribe to patients influenza antiviral drugs for a number of factors:
- low clinician awareness of CDC’s antiviral recommendations;
- a wide range in perception about how well these drugs work;
- some clinicians may require a positive flu test before prescribing antivirals (even though the results of rapid influenza diagnostic tests, if ordered, may not be accurate);
- and lastly, some physicians may not prescribe antivirals after the 2-day window during which benefit is optimal.
- CDC is working to understand clinicians’ concerns and improve awareness of the benefits offered by antivirals.