Historical annual reformulations of the influenza vaccine
Since 1999, the World Health Organization 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 2012-13 season, the WHO recommendations have also included the formulation of an annual quadrivalent vaccine, featuring an additional B-strain.
Northern hemisphere recommended strains
The following is a list of WHO recommended strains for the Northern Hemisphere influenza season. Starting in the 2012-2013 season, the recommendation shifted from a trivalent influenza vaccine containing three strains to a quadrivalent influenza vaccine that contains both influenza B lineages.| NH winter season | Influenza A H1N1 | Influenza A H3N2 | Influenza B Victoria | Influenza B Yamagata |
| November 1998–April 1999 | A/Beijing/262/95 -like virus | A/Sydney/5/97 -like virus | N/A | B/Beijing/184/93-like virus |
| November 1999–April 2000 | A/Beijing/262/95 -like virus | A/Sydney/5/97 -like virus | B/Shangdong/7/97-like virus | B/Beijing/184/93-like virus |
| 2000–2001 | A/New Caledonia/20/99 -like virus | A/Moscow/10/99 -like virus | N/A | B/Beijing/184/93-like virus |
| 2001–2002 | A/New Caledonia/20/99 -like virus | A/Moscow/10/99 -like virus | N/A | B/Sichuan/379/99-like virus |
| 2002–2003 | A/New Caledonia/20/99 -like virus | A/Moscow/10/99 -like virus | B/Hong Kong/330/2001-like virus | N/A |
| 2003–2004 | A/New Caledonia/20/99 -like virus | A/Moscow/10/99 -like virus | B/Hong Kong/330/2001-like virus | N/A |
| 2004–2005 | A/New Caledonia/20/99 -like virus | A/Fujian/411/2002 -like virus | N/A | B/Shanghai/361/2002-like virus |
| 2005–2006 | A/New Caledonia/20/99 -like virus | A/California/7/2004 -like virus | N/A | B/Shanghai/361/2002-like virus |
| 2006–2007 | A/New Caledonia/20/99 -like | A/Wisconsin/67/2005 -like virus | B/Malaysia/2506/2004-like virus | N/A |
| 2007–2008 | A/Solomon Islands/3/2006 -like virus | A/Wisconsin/67/2005 -like virus | B/Malaysia/2506/2004-like virus | N/A |
| 2008–2009 | A/Brisbane/59/2007 -like virus | A/Brisbane/10/2007 -like virus | N/A | B/Florida/4/2006-like virus |
| 2009–2010 | A/Brisbane/59/2007 -like virus | A/Brisbane/10/2007 -like virus | B/Brisbane/60/2008-like virus | N/A |
| 2010–2011 | A/California/7/2009 -like virus | A/Perth/16/2009 -like virus | B/Brisbane/60/2008-like virus | N/A |
| 2011–2012 | A/California/7/2009 -like virus | A/Perth/16/2009 -like virus | B/Brisbane/60/2008-like virus | N/A |
| 2012–2013 | A/California/7/2009 pdm09-like virus | A/Victoria/361/2011 -like virus | B/Brisbane/60/2008-like virus | B/Wisconsin/1/2010-like virus |
| 2013–2014 | A/California/7/2009 pdm09-like virus | A 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 pdm09-like virus | A/Texas/50/2012 -like virus | B/Brisbane/60/2008-like virus | B/Massachusetts/2/2012-like virus |
| 2015–2016 | A/California/7/2009 pdm09-like virus | A/Switzerland/9715293/2013 -like virus | B/Brisbane/60/2008-like virus | B/Phuket/3073/2013-like virus |
| 2016–2017 | A/California/7/2009 pdm09-like virus | A/Hong Kong/4801/2014 -like virus | B/Brisbane/60/2008-like virus | B/Phuket/3073/2013-like virus |
| 2017–2018 | A/Michigan/45/2015 pdm09-like virus | A/Hong Kong/4801/2014 -like virus | B/Brisbane/60/2008-like virus | B/Phuket/3073/2013-like virus |
| 2018–2019 | A/Michigan/45/2015 pdm09-like virus | A/Singapore/INFIMH-16-0019/2016 -like virus | B/Colorado/06/2017-like virus | B/Phuket/3073/2013-like virus |
| 2019–2020 | A/Brisbane/02/2018 pdm09-like virus | A/Kansas/14/2017 -like virus | B/Colorado/06/2017-like virus | B/Phuket/3073/2013-like virus |
| 2020–2021 Egg-based Vaccines | A/Guangdong-Maonan/SWL1536/2019 pdm09-like virus-like virus | A/Hong Kong/2671/2019 -like virus | B/Washington/02/2019 -like virus | B/Phuket/3073/2013 -like virus |
| 2020–2021 Cell- or recombinant-based Vaccines | A/Hawaii/70/2019 pdm09-like virus-like virus | A/Hong Kong/45/2019 -like virus | B/Washington/02/2019 -like virus | B/Phuket/3073/2013 -like virus |
Southern hemisphere recommended strains
The following is a list of WHO recommended strains for the southern hemisphere influenza season.| SH winter season | Influenza A H1N1 | Influenza A H3N2 | Influenza B Victoria | Influenza B Yamagata |
| 1999 | A/Beijing/262/95 -like virus | A/Sydney/5/97 -like virus | N/A | B/Beijing/184/93-like virus |
| May–October 2000 | A/New Caledonia/20/99 -like virus | A/Moscow/10/99 -like virus | B/Shangdong/7/97-like virus | B/Beijing/184/93-like virus |
| May–October 2001 | A/New Caledonia/20/99 -like virus | A/Moscow/10/99 -like virus | N/A | B/Sichuan/379/99-like virus |
| 2002 | A/New Caledonia/20/99 -like virus | A/Moscow/10/99 -like virus | N/A | B/Sichuan/379/99-like virus |
| 2003 | A/New Caledonia/20/99 -like virus | A/Moscow/10/99 -like virus | B/Hong Kong/330/2001-like virus | N/A |
| 2004 | A/New Caledonia/20/99 -like virus | A/Fujian/411/2002 - like virus | B/Hong Kong/330/2001-like virus | N/A |
| 2005 | A/New Caledonia/20/99 -like virus | A/Wellington/1/2004 -like virus | N/A | B/Shanghai/361/2002-like virus |
| 2006 | A/New Caledonia/20/99 -like virus | A/California/7/2004 -like virus | B/Malaysia/2506/2004-like virus | N/A |
| 2007 | A/New Caledonia/20/99 -like | A/Wisconsin/67/2005 -like virus | B/Malaysia/2506/2004-like virus | N/A |
| 2008 | A/Solomon Islands/3/2006 -like virus | A/Brisbane/10/2007 -like virus | N/A | B/Florida/4/2006-like virus |
| 2009 | A/Brisbane/59/2007 -like virus | A/Brisbane/10/2007 -like virus | N/A | B/Florida/4/2006-like virus |
| 2010 | A/California/7/2009 -like virus | A/Perth/16/2009 -like virus | B/Brisbane/60/2008-like virus | N/A |
| 2011 | A/California/7/2009 -like virus | A/Perth/16/2009 -like virus | B/Brisbane/60/2008-like virus | N/A |
| 2012 | A/California/7/2009 pdm09-like virus | A/Perth/16/2009 -like virus | B/Brisbane/60/2008-like virus | N/A |
| 2013 | A/California/7/2009 pdm09-like virus | A/Victoria/361/2011 -like virus | B/Brisbane/60/2008-like virus | B/Wisconsin/1/2010-like virus |
| 2014 | A/California/7/2009 pdm09-like virus | A/Texas/50/2012 -like virus | B/Brisbane/60/2008-like virus | B/Massachusetts/2/2012-like virus |
| 2015 | A/California/7/2009 pdm09-like virus | A/Switzerland/9715293/2013 -like virus | B/Brisbane/60/2008-like virus | B/Phuket/3073/2013-like virus |
| 2016 | A/California/7/2009 pdm09-like virus | A/Hong Kong/4801/2014 -like virus | B/Brisbane/60/2008-like virus | B/Phuket/3073/2013-like virus |
| 2017 | A/Michigan/45/2015 pdm09-like virus | A/Hong Kong/4801/2014 -like virus | B/Brisbane/60/2008-like virus | B/Phuket/3073/2013-like virus |
| 2018 | A/Michigan/45/2015 pdm09-like virus | A/Singapore/INFIMH-16-0019/2016 -like virus | B/Brisbane/60/2008-like virus | B/Phuket/3073/2013-like virus |
| 2019 | A/Michigan/45/2015 pdm09-like virus | A/Switzerland/8060/2017 -like virus | B/Colorado/06/2017-like virus | B/Phuket/3073/2013-like virus |
| 2020 | A/Brisbane/02/2018 pdm09-like virus | A/South Australia/34/2019 -like virus | B/Washington/02/2019-like virus | B/Phuket/3073/2013-like virus |