# Historical annual reformulations of the influenza vaccine

Since 1999, the World Health Organization (WHO) has issued annual recommendations for influenza vaccine formulations. One reformulation of the influenza vaccine is for the Northern Hemisphere, and the other is for the Southern Hemisphere. Both recommendations are trivalent, i.e. featuring three strains.
Since the 2012–2013 season, the WHO recommendations have also included the formulation of an annual quadrivalent vaccine, featuring an additional strain of Influenza B virus, B/Yamagata.
Due to the widespread use of non-pharmaceutical interventions at the beginning of the COVID-19 pandemic, the B/Yamagata influenza lineage has not been isolated since March 2020, and may have been eradicated. Starting with the 2024 Southern Hemisphere influenza season, the WHO and other regulatory bodies have removed this strain from influenza vaccine recommendations.

## Northern Hemisphere recommended strains

The following is a list of strains for the Northern Hemisphere influenza season recommended by the World Health Organization. Starting in the 2012–2013 season, the recommendation shifted to include the composition of a quadrivalent influenza vaccine (QIV) that contains both influenza B lineages, alongside a trivalent influenza vaccine (TIV) containing one influenza B lineage.
| NH winter season | Influenza A H1N1 | Influenza A H3N2 | Influenza B Victoria | Influenza B Yamagata |
| 1998–1999 | A/Beijing/262/95 (H1N1)-like virus | A/Sydney/5/97 (H3N2)-like virus | N/A | B/Beijing/184/93-like virus |
| 1999–2000 | A/Beijing/262/95 (H1N1)-like virus | A/Sydney/5/97 (H3N2)-like virus | B/Shangdong/7/97-like virus | B/Beijing/184/93-like virus |
| 2000–2001 | A/New Caledonia/20/99 (H1N1)-like virus | A/Moscow/10/99 (H3N2)-like virus | N/A | B/Beijing/184/93-like virus |
| 2001–2002 | A/New Caledonia/20/99 (H1N1)-like virus | A/Moscow/10/99 (H3N2)-like virus | N/A | B/Sichuan/379/99-like virus |
| 2002–2003 | A/New Caledonia/20/99 (H1N1)-like virus | A/Moscow/10/99 (H3N2)-like virus | B/Hong Kong/330/2001-like virus | N/A |
| 2003–2004 | A/New Caledonia/20/99 (H1N1)-like virus | A/Moscow/10/99 (H3N2)-like virus | B/Hong Kong/330/2001-like virus | N/A |
| 2004–2005 | A/New Caledonia/20/99 (H1N1)-like virus | A/Fujian/411/2002 (H3N2)-like virus | N/A | B/Shanghai/361/2002-like virus |
| 2005–2006 | A/New Caledonia/20/99 (H1N1)-like virus | A/California/7/2004 (H3N2)-like virus | N/A | B/Shanghai/361/2002-like virus |
| 2006–2007 | A/New Caledonia/20/99 (H1N1)-like virus | A/Wisconsin/67/2005 (H3N2)-like virus | B/Malaysia/2506/2004-like virus | N/A |
| 2007–2008 | A/Solomon Islands/3/2006 (H1N1)-like virus | A/Wisconsin/67/2005 (H3N2)-like virus | B/Malaysia/2506/2004-like virus | N/A |
| 2008–2009 | A/Brisbane/59/2007 (H1N1)-like virus | A/Brisbane/10/2007 (H3N2)-like virus | N/A | B/Florida/4/2006-like virus |
| 2009–2010 | A/Brisbane/59/2007 (H1N1)-like virus | A/Brisbane/10/2007 (H3N2)-like virus | B/Brisbane/60/2008-like virus | N/A |
| 2010–2011 | A/California/7/2009 (H1N1)-like virus | A/Perth/16/2009 (H3N2)-like virus | B/Brisbane/60/2008-like virus | N/A |
| 2011–2012 | A/California/7/2009 (H1N1)-like virus | A/Perth/16/2009 (H3N2)-like virus | B/Brisbane/60/2008-like virus | N/A |
| 2012–2013 | A/California/7/2009 (H1N1)pdm09-like virus | A/Victoria/361/2011 (H3N2)-like virus | B/Brisbane/60/2008-like virus | B/Wisconsin/1/2010-like virus |
| 2013–2014 | A/California/7/2009 (H1N1)pdm09-like virus | A(H3N2) virus antigenically like the cell-propagated prototype virus A/Victoria/361/2011 | B/Brisbane/60/2008-like virus | B/Massachusetts/2/2012-like virus |
| 2014–2015 | A/California/7/2009 (H1N1)pdm09-like virus | A/Texas/50/2012 (H3N2)-like virus | B/Brisbane/60/2008-like virus | B/Massachusetts/2/2012-like virus |
| 2015–2016 | A/California/7/2009 (H1N1)pdm09-like virus | A/Switzerland/9715293/2013 (H3N2)-like virus | B/Brisbane/60/2008-like virus | B/Phuket/3073/2013-like virus |
| 2016–2017 | A/California/7/2009 (H1N1)pdm09-like virus | A/Hong Kong/4801/2014 (H3N2)-like virus | B/Brisbane/60/2008-like virus | B/Phuket/3073/2013-like virus |
| 2017–2018 | A/Michigan/45/2015 (H1N1)pdm09-like virus | A/Hong Kong/4801/2014 (H3N2)-like virus | B/Brisbane/60/2008-like virus | B/Phuket/3073/2013-like virus |
| 2018–2019 | A/Michigan/45/2015 (H1N1)pdm09-like virus | A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus | B/Colorado/06/2017-like virus (B/Victoria/2/87 lineage) | B/Phuket/3073/2013-like virus (B/Yamagata/16/88 lineage) |
| 2019–2020 | A/Brisbane/02/2018 (H1N1)pdm09-like virus | A/Kansas/14/2017 (H3N2)-like virus | B/Colorado/06/2017-like virus (B/Victoria/2/87 lineage) | B/Phuket/3073/2013-like virus (B/Yamagata/16/88 lineage) |
| 2020–2021 egg-based vaccines | A/Guangdong-Maonan/SWL1536/2019 (H1N1)pdm09-like virus | A/Hong Kong/2671/2019 (H3N2)-like virus | B/Washington/02/2019 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2020–2021 cell- or recombinant-based vaccines | A/Hawaii/70/2019 (H1N1)pdm09-like virus | A/Hong Kong/45/2019 (H3N2)-like virus | B/Washington/02/2019 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2021–2022 egg-based vaccines | A/Victoria/2570/2019 (H1N1)pdm09-like virus | A/Cambodia/e0826360/2020 (H3N2)-like virus | B/Washington/02/2019 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2021–2022 cell- or recombinant-based vaccines | A/Wisconsin/588/2019 (H1N1)pdm09-like virus | A/Cambodia/e0826360/2020 (H3N2)-like virus | B/Washington/02/2019 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2022–2023 egg-based vaccines | A/Victoria/2570/2019 (H1N1)pdm09-like virus | A/Darwin/9/2021 (H3N2)-like virus | B/Austria/1359417/2021 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2022–2023 cell- or recombinant-based vaccines | A/Wisconsin/588/2019 (H1N1)pdm09-like virus | A/Darwin/6/2021 (H3N2)-like virus | B/Austria/1359417/2021 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2023–2024 egg-based vaccines | A/Victoria/4897/2022 (H1N1)pdm09-like virus | A/Darwin/9/2021 (H3N2)-like virus | B/Austria/1359417/2021 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2023–2024 cell- or recombinant-based vaccines | A/Wisconsin/67/2022 (H1N1)pdm09-like virus | A/Darwin/6/2021 (H3N2)-like virus | B/Austria/1359417/2021 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2024–2025 egg-based vaccines | A/Victoria/4897/2022 (H1N1)pdm09-like virus | A/Thailand/8/2022 (H3N2)-like virus | B/Austria/1359417/2021 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2024–2025 cell- or recombinant-based vaccines | A/Wisconsin/67/2022 (H1N1)pdm09-like virus | A/Massachusetts/18/2022 (H3N2)-like virus | B/Austria/1359417/2021 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2025–2026 egg-based vaccines | A/Victoria/4897/2022 (H1N1)pdm09-like virus | A/Croatia/10136RV/2023 (H3N2)-like virus | B/Austria/1359417/2021 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2025–2026 cell- or recombinant-based vaccines | A/Wisconsin/67/2022 (H1N1)pdm09-like virus | A/District of Columbia/27/2023 (H3N2)-like virus | B/Austria/1359417/2021 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |

## Southern Hemisphere recommended strains

The following is a list of strains for the Southern Hemisphere influenza season recommended by the World Health Organization.
| SH winter season | Influenza A H1N1 | Influenza A H3N2 | Influenza B Victoria | Influenza B Yamagata |
| 1999 | A/Beijing/262/95 (H1N1)-like virus | A/Sydney/5/97 (H3N2)-like virus | N/A | B/Beijing/184/93-like virus |
| 2000 | A/New Caledonia/20/99 (H1N1)-like virus | A/Moscow/10/99 (H3N2)-like virus | B/Shangdong/7/97-like virus | B/Beijing/184/93-like virus |
| 2001 | A/New Caledonia/20/99 (H1N1)-like virus | A/Moscow/10/99 (H3N2)-like virus | N/A | B/Sichuan/379/99-like virus |
| 2002 | A/New Caledonia/20/99 (H1N1)-like virus | A/Moscow/10/99 (H3N2)-like virus | N/A | B/Sichuan/379/99-like virus |
| 2003 | A/New Caledonia/20/99 (H1N1)-like virus | A/Moscow/10/99 (H3N2)-like virus | B/Hong Kong/330/2001-like virus | N/A |
| 2004 | A/New Caledonia/20/99 (H1N1)-like virus | A/Fujian/411/2002 (H3N2)-like virus | B/Hong Kong/330/2001-like virus | N/A |
| 2005 | A/New Caledonia/20/99 (H1N1)-like virus | A/Wellington/1/2004 (H3N2)-like virus | N/A | B/Shanghai/361/2002-like virus |
| 2006 | A/New Caledonia/20/99 (H1N1)-like virus | A/California/7/2004 (H3N2)-like virus | B/Malaysia/2506/2004-like virus | N/A |
| 2007 | A/New Caledonia/20/99 (H1N1)-like virus | A/Wisconsin/67/2005 (H3N2)-like virus | B/Malaysia/2506/2004-like virus | N/A |
| 2008 | A/Solomon Islands/3/2006 (H1N1)-like virus | A/Brisbane/10/2007 (H3N2)-like virus | N/A | B/Florida/4/2006-like virus |
| 2009 | A/Brisbane/59/2007 (H1N1)-like virus | A/Brisbane/10/2007 (H3N2)-like virus | N/A | B/Florida/4/2006-like virus |
| 2010 | A/California/7/2009 (H1N1)-like virus | A/Perth/16/2009 (H3N2)-like virus | B/Brisbane/60/2008-like virus | N/A |
| 2011 | A/California/7/2009 (H1N1)-like virus | A/Perth/16/2009 (H3N2)-like virus | B/Brisbane/60/2008-like virus | N/A |
| 2012 | A/California/7/2009 (H1N1)pdm09-like virus | A/Perth/16/2009 (H3N2)-like virus | B/Brisbane/60/2008-like virus | N/A |
| 2013 | A/California/7/2009 (H1N1)pdm09-like virus | A/Victoria/361/2011 (H3N2)-like virus | B/Brisbane/60/2008-like virus | B/Wisconsin/1/2010-like virus |
| 2014 | A/California/7/2009 (H1N1)pdm09-like virus | A/Texas/50/2012 (H3N2)-like virus | B/Brisbane/60/2008-like virus | B/Massachusetts/2/2012-like virus |
| 2015 | A/California/7/2009 (H1N1)pdm09-like virus | A/Switzerland/9715293/2013 (H3N2)-like virus | B/Brisbane/60/2008-like virus | B/Phuket/3073/2013-like virus |
| 2016 | A/California/7/2009 (H1N1)pdm09-like virus | A/Hong Kong/4801/2014 (H3N2)-like virus | B/Brisbane/60/2008-like virus | B/Phuket/3073/2013-like virus |
| 2017 | A/Michigan/45/2015 (H1N1)pdm09-like virus | A/Hong Kong/4801/2014 (H3N2)-like virus | B/Brisbane/60/2008-like virus | B/Phuket/3073/2013-like virus |
| 2018 | A/Michigan/45/2015 (H1N1)pdm09-like virus | A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus | B/Brisbane/60/2008-like virus | B/Phuket/3073/2013-like virus |
| 2019 | A/Michigan/45/2015 (H1N1)pdm09-like virus | A/Switzerland/8060/2017 (H3N2)-like virus | B/Colorado/06/2017-like virus (B/Victoria/2/87 lineage) | B/Phuket/3073/2013-like virus (B/Yamagata/16/88 lineage) |
| 2020 | A/Brisbane/02/2018 (H1N1)pdm09-like virus | A/South Australia/34/2019 (H3N2)-like virus | B/Washington/02/2019-like (B/Victoria lineage) virus | B/Phuket/3073/2013-like (B/Yamagata lineage) virus |
| 2021 egg-based vaccines | A/Victoria/2570/2019 (H1N1)pdm09-like virus | A/Hong Kong/2671/2019 (H3N2)-like virus | B/Washington/02/2019 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2021 cell- or recombinant-based vaccines | A/Wisconsin/588/2019 (H1N1)pdm09-like virus | A/Hong Kong/45/2019 (H3N2)-like virus | B/Washington/02/2019 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2022 egg-based vaccines | A/Victoria/2570/2019 (H1N1)pdm09-like virus | A/Darwin/9/2021 (H3N2)-like virus | B/Austria/1359417/2021 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2022 cell- or recombinant-based vaccines | A/Wisconsin/588/2019 (H1N1)pdm09-like virus | A/Darwin/6/2021 (H3N2)-like virus | B/Austria/1359417/2021 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2023 egg-based vaccines | A/Sydney/5/2021 (H1N1)pdm09-like virus | A/Darwin/9/2021 (H3N2)-like virus | B/Austria/1359417/2021 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2023 cell- or recombinant-based vaccines | A/Sydney/5/2021 (H1N1)pdm09-like virus | A/Darwin/6/2021 (H3N2)-like virus | B/Austria/1359417/2021 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2024 egg-based vaccines | A/Victoria/4897/2022 (H1N1)pdm09-like virus | A/Thailand/8/2022 (H3N2)-like virus | B/Austria/1359417/2021 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |
| 2024 cell- or recombinant-based vaccines | A/Wisconsin/67/2022 (H1N1)pdm09-like virus | A/Massachusetts/18/2022 (H3N2)-like virus | B/Austria/1359417/2021 (B/Victoria lineage)-like virus | B/Phuket/3073/2013 (B/Yamagata lineage)-like virus |