CDC: 2016-2017 Flu Vaccine Nearly 50 Percent Effective

February 21, 2017 01:26 pm News Staff

The CDC issued a Morbidity and Mortality Weekly Report(www.cdc.gov) (MMWR) Feb. 17 that said interim estimates from U.S. Flu Vaccine Effectiveness Network data for the 2016-2017 influenza season showed this year's flu vaccine has been 48 percent effective in preventing laboratory-confirmed influenza A and B viral infection associated with medically attended acute respiratory illness.

The exact interim effectiveness estimates are 43 percent against the predominant influenza A (H3N2) viruses and 73 percent against influenza B viruses, said the MMWR.

Story highlights
  • The CDC released interim estimates for the 2016-2017 influenza season that show this year's vaccine has been 48 percent effective in preventing laboratory-confirmed influenza A and B viral infection associated with medically attended acute respiratory illness.
  • Interim effectiveness estimates are 43 percent against the predominant influenza A (H3N2) viruses and 73 percent against influenza B viruses.
  • The CDC said the Midwest and East Coast continue to see increased flu rates, while case numbers in the Northwest previously spiked and have since been declining.

According to a Feb. 16 flu news report(www.cdc.gov) from the agency, those interim estimates are consistent with vaccine effectiveness (VE) estimates from previous seasons during which vaccine viruses have been characterized as being well-matched to circulating viruses based on standard characterization methods. 

Since 2010, the CDC has published annual estimates of the number of illnesses, medical visits and hospitalizations prevented by vaccination each year.

"While those estimates are not yet available for the current season, the CDC estimated that during 2012-2013, an H3N2-predominant season with overall VE of 49 percent, flu vaccine prevented 5.6 million flu illnesses, 2.7 million flu-related medical visits and about 61,500 flu hospitalizations," said the news report.

The news report also noted that general flu activity has been elevated for eight weeks, and some areas are continuing to see increased activity.

Specifically, said another MMWR issue(www.cdc.gov) released Feb. 17 that summarized influenza activity from Oct. 2 to Feb. 4, the Midwest and East Coast continue to see increased flu rates, while incidents in the Northwest previously spiked and have since been declining.

2016-2017 Novel Influenza Viruses

In a Morbidity and Mortality Weekly Report(www.cdc.gov) (MMWR) released Feb. 17 that summarized influenza activity and virologic surveillance data from Oct. 2 to Feb. 4, the CDC reported on two separate cases of human infection with novel influenza A viruses.

The first instance involved a single case of infection with an influenza A (H1N2) variant in a person with exposure to swine the week preceding illness onset. The second was linked to an outbreak of avian lineage influenza A (H7N2) virus infection among cats in an animal shelter in New York City.

That outbreak(www1.nyc.gov), which involved more than 100 cats, was first reported to public health officials on Dec. 14. About 350 people who were exposed to the infected cats were screened or tested for infection; only one human infection was detected in a veterinarian who treated the cats.

Neither of the two patients was hospitalized, and both have since completely recovered. No human-to-human transmission has been documented.  

CDC officials said that even though only weeks remain in this influenza season, patients who get vaccinated now will still be better protected against illness, particularly in light of a small uptick recently seen in influenza B virus activity. Past influenza seasons have stretched as late as into May, and patients can benefit from vaccination as long as influenza viruses continue to circulate.

Patients who do acquire an influenza virus should be treated with antiviral medications. No antiviral resistance to oseltamivir (Tamiflu), zanamivir (Relenza) or peramivir (Rapivab) has been identified among influenza viruses collected since Oct. 1, said the agency.

The CDC recommends early antiviral treatment for patients with suspected influenza who have severe or progressive illness (e.g., hospitalized patients), as well as for people at high risk for complications from influenza, such as children younger than age 5, adults 65 and older, and patients with underlying health conditions -- even if their illness is less severe.

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