So far this flu season, more than two-thirds of influenza A (H3N2) viruses differ from the components of the 2014-2015 influenza vaccine. In addition, the overall estimated effectiveness of the 2014-2015 influenza vaccine for preventing laboratory-confirmed influenza infection is only 23%.
Those are key findings from an analysis of 2,321 children and adults who presented to one of five study sites in the United States with acute respiratory illness between Nov. 10, 2014, and Jan. 2, 2015.
“Although influenza vaccines are the best tool for prevention of influenza currently available, more effective vaccines are needed,” wrote Brendan Flannery, Ph.D., of the influenza division at the CDC’s National Center for Immunization and Respiratory Disease, and his associates. The report is in the Jan. 16, 2015, issue of the CDC’s Morbidity and Mortality Weekly Report (MMWR 2015 Jan. 16;64:10-15). “Antiviral medications are an important adjunct in the treatment and control of influenza for the 2014-2015 season and should be used as recommended, regardless of patient vaccination status.”
Targeted groups for antiviral treatment include any patient with suspected or confirmed influenza who is hospitalized, has severe or progressive illness, or is at high risk for complications from influenza, even if the illness seems mild. “Persons at high risk include young children (especially those younger than age 2), pregnant women, persons with chronic medical conditions like asthma, diabetes, or heart disease, and adults aged 65 years and older,” the researchers wrote. “Ideally, antiviral treatment should be initiated within 48 hours of symptom onset, when treatment is most effective.”
Though spot shortages of Tamiflu and other antiviral drugs have been reported in the United States, the CDC investigators noted that it may be necessary for physicians and patients to contact more than one pharmacy to fill a prescription. Updates on the supply of antiviral drugs can be found here.
Dr. Flannery and his associates acknowledged certain limitations of their analysis, including the fact that future estimates could differ as more data become available and that the current estimates “are limited to the prevention of outpatient medical visits, rather than more severe illness outcomes, such as hospitalization or death.”
The researchers reported having no relevant financial conflicts.
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