What does it mean when the Influenza Virus “drifts”?

When Influenza Virus “Drifts”

  • Vaccines for each year’s flu are formulated months in advance to allow time for vaccine manufacturing and distribution.
    • 100 centers around the world provide influenza surveillance and predict which strains will circulate to the US and North America. Decisions are made in February each year for the next year’s vaccine. Researchers look at trends to determine which viruses may be more prevalent.
    • The vaccine (the shot) protects against three (trivalent vaccine) or four flu viruses (the mist),(quadrivalent vaccine), based on the world’s predictions. Typically each flu vaccine has at least two strains of Influenza A and one or two strains of Influenza B. Of anything that is consistent it’s that flu seasons are unpredictable.
  • H3N2 is one strain of Influenza A in this year’s vaccine. The “drifted” vaccine is just another form of H3N2 that has different characteristics.
    • Flu viruses often “drift,” this happens every few years. The drifted H3N2 virus is one specific type selected for the 2015 southern hemisphere influenza vaccine (point being: this isn’t an unknown virus, it was just unknown how much it would spread in the US).

Should You Still Get A Flu Shot?

  • You should still get a vaccinated against influenza via the shot or nasal spray as it’s the most effective prevention tool. Circulating H3N2 and H1N1 strains we are also seeing are in the vaccine, as is the Influenza B strain. In addition, “cross-protection” is likely from the H3N2 in the vaccine for the southern hemisphere strain. Translation: it’s likely the protection you get from the shot will help decrease effects of infections by strains not included in the vaccine.
    • The CDC recommends getting the flu shot or nasal spray as soon as possible to protect yourself and your family. Now is a great time!
    • The nasal spray vaccine is still preferential for healthy children ages 2 – 8. Here’s a detailed post explaining why:
      • This year it’s know that the nasal spray isn’t as effective against the 2009 H1N1 strain, but very little H1N1 is circulating.
      • Get the shot if spray isn’t available. Waiting is not recommended.

Getting Medications For Influenza?

  • Flu shot is still available and recommended, as long as flu is spreading and causing illness the flu vaccine should continue.
  • A big part of the CDC recommendations this past week were about informing the public to seek care if suspected influenza hits. It’s important to see the nurse or physician if you have suspected influenza on day 1 or 2, especially if you are high-risk. Oral medication (Tamiflu or Relenza) can decrease your symptoms, shorten the illness, and prevent serious complications. Call for an appointment if flu symptoms or concern for flu especially
    • Antiviral treatment recommended for high-risk patients:
      • Children under 2 years
      • Adults over 65
      • Pregnant women
      •  Anyone with complicated/severe illness
  • Be smart, like you are, of course!
    • Wash your hands, cough into your elbow, stay home when sick!
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