WHO Consultation and Information Meeting held from February 19-21, 2018, at Geneva, Switzerland has recommended the composition of influenza virus vaccines for use in the Northern Hemisphere Influenza Season, 2018-2019. As the periodic replacement of viruses contained in influenza vaccines is necessary in order for the vaccines to be effective due to the constant evolving nature of influenza viruses, including those circulating and infecting humans.

WHO Consultation and Information Meeting which meets twice annually, in the February 2018 meeting designed to –

  • Review of the global influenza activity;
  • Analysis of results of vaccine serological studies;
  • Recommendations for the composition of influenza virus vaccines for use in the Northern Hemisphere Influenza season, 2018-2019;
  • Review of the need and subsequent selection of new A (H7N9), A (H5) and other subtype or variant viruses for the development of new candidate vaccine viruses for pandemic preparedness purposes.

WHO recommended Quadrivalent Influenza vaccines:

WHO Consultation and Information Meeting has recommended quadrivalent vaccines for use in the 2018-2019 northern hemisphere influenza season36 which contains the following viruses:

  • An A/Michigan/45/2015 (H1N1)pdm09-like virus;
  • An A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus;
  • A B/Colorado/06/2017-like virus (B/Victoria/2/87 lineage); and
  • A B/Phuket/3073/2013-like virus (B/Yamagata/16/88 lineage).

It is recommended that trivalent vaccines contain the B/Colorado/06/2017-like virus, of the B/Victoria/2/87- lineage.

The influenza B/Victoria lineage virus component and the A (H3N2) virus component have been updated compared to the viruses recommended for the 2017-2018 northern hemisphere influenza seasons. The update is as follows:

  • yy Replacement of the A/Hong Kong/4801/2014 (H3N2)-like virus with an A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus.
  • yy Replacement of the B/Brisbane/60/2008-like virus with a B/Colorado/06/2017-like virus.

Recommendation for northern or southern hemisphere influenza season:

Influenza viruses circulate at varying times through the year in tropical and sub-tropical countries. In selecting which vaccine formulation to use, these countries should consider their surveillance information, in particular epidemiological and virological data to decide when to start vaccination and whether to use the formulation recommended for the northern or southern hemisphere influenza season. WHO has formulated guidance for countries in tropical and sub-tropical regions to assist them in choosing which vaccine composition (February/ March or September) is most appropriate37.

Development of Candidate Vaccine Viruses (CVVs): WHO Consultation and Information Meeting provides a review on the zoonotic influenza virus activity and virus characterization, and describes the current status of the development of CVVs for pandemic preparedness purposes38. It is meant to provide guidance for national authorities and vaccine companies on the selection of candidate viruses for use in vaccine development.

Influenza A (H5)

Since their emergence in 1997, highly pathogenic avian influenza (HPAI) A (H5) viruses of the A/goose/ Guangdong/1/96 haemagglutinin (HA) lineage have become enzootic in some countries, have infected wild birds and continue to cause outbreaks in poultry and sporadic human infections. These viruses have diversified genetically and antigenically, including the emergence of viruses with replacement of the N1 gene segment by N2, N3, N5, N6, N8 or N9 gene segments, leading to the need for multiple CVVs. For example- recent A (H5) activity in India is hosted by Poultry with Genetic clade (subtype): 2.3.4.4 (H5N8), and the recent A (H5) activity in United Kingdom is hosted by wild birds with genetic clade (Subtype): 2.3.4.4 (H5N6). Therefore –

  • The development of influenza candidate vaccine viruses (CVVs), coordinated by WHO, remains an essential component of the overall global strategy for pandemic preparedness.
  • Selection and development of CVVs are the first steps towards timely vaccine production and do not imply a recommendation for initiating manufacture. National authorities may consider the use of one or more of these CVVs for pilot lot vaccine production, clinical trials and other pandemic preparedness purposes based on their assessment of public health risk and need.
  • Zoonotic influenza viruses continue to be identified and evolve both genetically and antigenically, leading to the need for additional CVVs for pandemic preparedness purposes. Changes in the genetic and antigenic characteristics of these viruses relative to existing CVVs, and their potential risks to public health, justify the need to select and develop new CVVs39.

Conclusion:

WHO recommendations and updates on list of CVVs are used by the national vaccine regulatory agencies and the pharmaceutical companies to develop, produce and license influenza vaccines. Further, approval of the composition and formulation of vaccines that will be used in each country is the responsibility of national or regional regulatory authorities. However, it is the responsibility of the vaccine manufacturer to obtain the appropriate CVVs and to obtain approval from the local regulatory agency.

Footnotes

37 http://www.who.int/influenza/vaccines/virus/recommendations/201802_qanda_recommendation.pdf

38 http://www.who.int/influenza/vaccines/virus/201802_zoonotic_vaccinevirusupdate.pdf

39 http://www.who.int/influenza/vaccines/virus/201802_zoonotic_vaccinevirusupdate.pdf

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