What are the components of the 2019-2020 Northern Hemisphere seasonal influenza vaccines?

Updated: Apr 23, 2019
  • Author: Hien H Nguyen, MD, MS; Chief Editor: Michael Stuart Bronze, MD  more...
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Two of the vaccine viral strains recommended by the World Health Organization and the Centers for Disease Control and Prevention (CDC) for the 2019-2020 Northern Hemisphere influenza season differ from those from the previous influenza season. [8]

The trivalent 2019-2020 Northern Hemisphere vaccine season contains the following components:

  • A/Brisbane/02/2018 (H1N1)pdm09-like virus (new for 2019-2020)
  • A/Kansas/14/2017 (H3N2)-like virus (new for 2019-2020)
  • B/Colorado/06/2017-like virus (B/Victoria/2/87 lineage) (no change from preceding season)

The quadrivalent influenza vaccines contain an additional B strain, B/Phuket/3073/2013-like virus (B/Yamagata lineage) (no change from prior season), in addition to the 3 viral strains listed above.

In February 2019, the CDC reported that the 2018-2019 influenza vaccine appeared to be more effective than the 2017-2018 flu vaccine, decreasing office visits for flu-related illness by approximately 47% overall and by 61% in children aged 6 months to 17 years. At that time, they reported that the predominant flu strains were H1N1 in most of the United States and H3N2 in southeastern areas of the country. [52] In March 2019, the CDC reported that H3N2 had become the predominant strain in much of the United States, increasing the number of pediatric flu-related deaths. [53]

Injectable vaccine, which contains inactivated virus, is available in a variety of dosage forms. The intramuscular (IM) form contains 45 µg of influenza hemagglutinin per 0.5 mL. A microinjection system for intradermal delivery (Fluzone Intradermal) is available in the United States and features an ultrafine needle that is 90% shorter than the typical 1- to 1.5-inch needle used for IM injections. The intradermal dosage form contains 27 µg of influenza hemagglutinin per 0.1 mL. A recombinant influenza vaccine (Flublok) that contains no egg proteins, antibiotics, or preservatives is also available as both trivalent and quadrivalent formulations. [9] Adults aged 65 years or older may receive a high-dose inactivated influenza vaccine (Fluzone High-Dose). [54]

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