A report published in the Jan. 16, 2015 edition of the Morbidity and Mortality Weekly Report (MMWR) estimates that this season’s flu vaccine reduced a person’s risk of going to the doctor because of flu by 23 percent for all ages. The MMWR report states the reduced protection offered by flu vaccine this season underscores the need for additional prevention and treatment efforts, including the appropriate use of influenza antiviral medications for treatment.
Antiviral influenza medications are effective in treating the flu and reducing complications, and are critical tools for reducing the burden of flu illness. Unfortunately, evidence from previous and the current flu season suggest that flu antiviral drugs are severely underused. One recent study by Havers, et al. reported that only 19 percent of high-risk outpatients who would benefit the most from and who should have gotten treated with flu antivirals actually did.
Current Flu Vaccine Effectiveness
Since CDC began conducting annual flu vaccine effectiveness (VE) studies in 2004-2005, overall estimates for each season have ranged from 10 percent to 60 percent effectiveness in preventing medical visits associated with seasonal influenza illness.
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, VE 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 VE.
CDC has done limited qualitative research into clinician knowledge, attitudes and practices related to anti-influenza drugs. The findings suggest that there are probably a number of factors involved. These include:
- 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)
- some physicians may not prescribe antivirals after the two-day window during which benefit is optimal.
The CDC is working to understand clinicians’ concerns and improve awareness of the benefits offered by antivirals.
Messages to Clinicians
CDC's antiviral recommendations are summarized in Influenza Antiviral Medications: Summary for Clinicians, and are also available in CDC Health Update Regarding Treatment of Patients with Influenza with Antiviral Medications (distributed Jan. 9, 2015).
Note the following important messages:
1. Influenza activity is currently widespread, so influenza should be high on the list of possible diagnoses for ill patients.
2. All hospitalized, severely ill and high risk patients with suspected influenza should be treated with antivirals.
3. CDC recommends antiviral medications for treatment of influenza as an important adjunct to annual influenza vaccination. Treatment with antivirals has been shown to have clinical and public health benefit in reducing illness and severe outcomes of influenza, as evidenced from randomized controlled trials, meta-analyses of randomized controlled trials, and observational studies conducted during past influenza seasons and during the 2009 H1N1 pandemic. All hospitalized patients and all high-risk patients (either hospitalized or outpatient) with suspected influenza should be treated as soon as possible with one of three available influenza antiviral medications.
4. Antiviral treatment should commence regardless of a patient’s vaccination status, and without waiting for influenza confirmatory testing.
5. While antiviral drugs work best when given early, therapeutic benefit has been observed even when treatment is initiated later for some patients.
Resources for Patient Education
Results from unpublished CDC qualitative research shows that most people interviewed were not aware that drugs to treat influenza illness are available. Patients being provided a prescription for an influenza antiviral drug may have questions. A fact sheet for patients is available.
Note the following important background information for patients:
- If you get the flu, antiviral drugs are a treatment option.
- It is very important that antiviral drugs are used early to treat hospitalized patients, people with severe flu illness, and people who are at high risk for flu complications because of their age, severity of illness, or underlying medical conditions.
- If you have severe illness or are at high risk of serious flu complications, you may be treated with flu antiviral drugs if you get the flu.
- For people with a high-risk condition, treatment with an antiviral drug can mean the difference between having milder illness instead of very serious illness that could result in a hospital stay.
- Other people also may be treated with antiviral drugs by their doctor this season. Most otherwise-healthy people who get the flu, however, do not need to be treated with antiviral drugs.
- Studies show that flu antiviral drugs work best for treatment when they are started within two days of getting sick. However, starting antivirals later can still be helpful for some people.
- If your healthcare provider thinks you have the flu, your health are provider may prescribe antiviral drugs. A test for flu is not necessary.
- Antibiotics are not effective against the flu. Using antibiotics inappropriately can lead to antibiotic resistance and may expose patients to unwanted side effects of the drug.
- Other practices that may help decrease the spread of influenza include respiratory hygiene, cough etiquette, social distancing (e.g., staying home from work and school when ill, staying away from people who are sick) and handwashing.