Atlanta—The current influenza vaccine has an overall effectiveness of 45%, putting it in line with previous flu seasons, according to an interim estimate from the CDC.

That information comes from U.S. Influenza Vaccine Effectiveness Network data including 4,112 children and adults with acute respiratory illness from October 23, 2019, to January 25, 2020. The CDC looked at the overall estimated effectiveness of seasonal influenza vaccine for preventing medically attended, laboratory-confirmed influenza virus infection.

Vaccine effectiveness (VE) was estimated to be 50% (95% CI, 39%-59%) against influenza B/Victoria viruses and 37% (95% CI, 19%-52%) against influenza A(H1N1)pdm09. The article in Morbidity & Mortality Weekly Report states that those statistics indicate the vaccine has significantly reduced medical visits associated with influenza so far this season.

The vaccine was especially protective, with a VE of 55%, among children and adolescents aged 6 months to 17 years, according to the report.

“Interim VE estimates are consistent with those from previous seasons, ranging from 40%–60% when influenza vaccines were antigenically matched to circulating viruses,” points out the CDC, which recommends that pharmacists and other healthcare providers continue to administer influenza vaccine to those aged 6 months old and older because influenza activity is ongoing. It emphasizes that the vaccine can still prevent illness, hospitalization, and death associated with currently circulating influenza viruses, as well as other influenza viruses that might circulate later in the season.

“The 2019–20 influenza season began early with predominant influenza B/Victoria virus circulation, followed by increasing A(H1N1)pdm09 virus activity, with ongoing detection of both viruses,” the authors write, noting that flu activity remained elevated in most parts of the country in February.

The CDC cautions that, in some ways, this has been a troubling flu season, explaining, “Markers of severe illness, including laboratory-confirmed influenza-associated hospitalization rates among children and adolescents aged <18 years and young adults aged 18–49 years, are higher than at this time in recent seasons, including the 2017–18 season. To date for this season, 92 influenza-associated deaths have been reported in children and adolescents aged <18 years; other than the 2009 pandemic, this is the largest number reported for this time of the season since reporting began for the 2004–05 influenza season.”

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