Effectiveness of the 2023 Southern Hemisphere Influenza Vaccine Against Outpatient Influenza-Like Illness: A Multi-Country Test-Negative Design Study - Takeaways - MDSpire

Effectiveness of the 2023 Southern Hemisphere Influenza Vaccine Against Outpatient Influenza-Like Illness: A Multi-Country Test-Negative Design Study

  • By

  • Annette K Regan

  • Radhika Gharpure

  • Monique Chilver

  • Nigel Stocks

  • Siobhan St George

  • Sibongile Walaza

  • Anne von Gottberg

  • Nicole Wolter

  • Cheryl Cohen

  • Aaron M Samuels

  • Kriengkrai Prasert

  • Prabda Praphasiri

  • William W Davis

  • Chakrarat Pittayawonganon

  • Sheena G Sullivan

  • Eduardo Azziz-Baumgartner

  • September 17, 2025

  • 0 min

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  • 1

    The 2023 Southern Hemisphere influenza vaccine showed a pooled effectiveness of 68% against influenza-like illness in Australia, South Africa, and Thailand.

  • 2

    Influenza A viruses accounted for 78% of test-positive cases, with 39% of patients presenting with influenza-like illness testing positive for the virus.

  • 3

    Vaccine effectiveness was 76% against influenza B, 62% against A(H1N1)pdm09, and 60% against A(H3N2), indicating varied protection across virus types.

  • 4

    Vaccine effectiveness declined from 82% to 43% as the interval between vaccination and symptom onset increased from 14 to 150 days.

  • 5

    The study underscores the importance of seasonal influenza vaccination programs in reducing the burden of influenza-related illnesses.

Original Source(s)

Effectiveness of the 2023 Southern Hemisphere Influenza Vaccine Against Outpatient Influenza-Like Illness: A Multi-Country Test-Negative Design Study

  • by Annette K Regan, Radhika Gharpure, Monique Chilver, Nigel Stocks, Siobhan St George, Sibongile Walaza, Anne von Gottberg, Nicole Wolter, Cheryl Cohen, Aaron M Samuels, Kriengkrai Prasert, Prabda Praphasiri, William W Davis, Chakrarat Pittayawonganon, Sheena G Sullivan, Eduardo Azziz-Baumgartner

  • September 17, 2025

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