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State of California—Health and Human Services Agency
California Department of Public Health

May 17, 2022

Health Care Providers

Health Advisory: Seasonal Influenza Activity is Increasing in California May 17, 2022

​CDPH is notifying health care providers that seasonal influenza activity is gradually increasing, with elevated activity in Central California. This advisory provides guidance regarding vaccination, testing, and antiviral treatment in the context of co-circulation of influenza and SARS-CoV-2. Influenza vaccination remains reasonable, especially for persons at high risk of severe influenza. Influenza testing and influenza antiviral treatment are recommended in specific clinical scenarios.

Key Messages

  • Seasonal influenza activity in California has been increasing gradually for several weeks. Activity is elevated in Central California.
    • Influenza A (H3N2) viruses are predominant, but influenza B viruses have also been detected.
    • Influenza hospitalizations are also increasing.
  • If influenza vaccine is still available, continue to recommend:
    • Influenza vaccination, particularly to patients at high risk of severe influenza.
    • Coadministration of influenza and COVID-19 vaccine when patients present for either vaccine separately.
  • Interim vaccine effectiveness results from CDC's U.S. Flu Vaccine Effectiveness Network indicate that vaccination did not reduce the risk of mild to moderate illness from these H3N2 viruses. However, it is reasonable to continue to vaccinate as long as influenza viruses are circulating and even when protection against one virus is reduced.
    • Influenza vaccines protect against four different influenza viruses and vaccination may prevent serious outcomes in people who are vaccinated but still get sick.
    • While the results of influenza vaccine effectiveness studies against severe outcomes are still to come, vaccination has been shown in several past studies to reduce severity of influenza in people who get vaccinated but still get sick.
    • Persons who receive a late-season influenza vaccine will still be eligible for a 2022-23 seasonal influenza vaccine at the usual time.
  • Testing
    • In general, all persons tested for influenza should also be tested for SARS-CoV-2.
    • Inpatient and congregate settings: Test all persons with respiratory illnesses.
    • Outpatient settings: Test all persons with respiratory illness for SARS-CoV-2. Test for influenza when it will affect clinical management or infection control.
  • Provide influenza antiviral treatment as soon as possible to any patient with confirmed or suspected influenza who is
  • For high-risk persons with influenza-like illness:
    • Test for both influenza and SARS-CoV-2.
    • Start influenza antiviral treatment immediately. Do not wait for laboratory confirmation.
    • If the patient tests negative for influenza, discontinue influenza antiviral treatment.
    • If the patient tests positive for SARS-CoV-2, SARS-CoV-2 treatment (either with an anti-SARS-CoV-2 monoclonal antibody or authorized antiviral treatment) should be considered in outpatients at high risk for disease progression as outlined in product EUAs.
    • Treat both influenza and SARS-CoV-2 when co-infection is present.
  • Suspected or laboratory-confirmed influenza outbreaks in long-term care facilities should be reported to the local health department. Mitigation measures, including influenza antiviral post-exposure prophylaxis may be recommended.
  • Besides getting immunized, other everyday actions can stop the spread of respiratory viruses:
    • Continue to wear a mask when recommended or required in high-risk settings.
    • Stay away from people who are sick.
    • Stay home when sick.
    • Cough or sneeze into your elbow, arm, or disposable tissue. If disposable tissue is used, use hand sanitizer or wash hands afterwards.
    • Wash hands frequently and thoroughly with soap and warm water or use an alcohol-based hand sanitizer.
    • Avoid touching your eyes, nose, and mouth.

Influenza Resources

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