Vaccination remains the most effective means of preventing infection by seasonal influenza viruses and can reduce severe disease that can lead to hospitalisation and death.
The influenza vaccine is most effective when circulating viruses are well-matched with viruses contained in vaccines. Due to the constant evolving nature of influenza viruses, the WHO Global Influenza Surveillance and Response System – a system of National Influenza Centres and WHO Collaborating Centres around the world – continuously monitors the influenza viruses circulating in humans and updates the composition of influenza vaccines twice a year. These recommendations are used by national vaccine regulatory agencies and pharmaceutical companies to develop, produce and license influenza vaccines.
The influenza vaccine purchased by the HSE is based on WHO advice. Composition of influenza virus vaccines for use in the northern hemisphere during the flu season is given for both quadrivalent and trivalent vaccines. Trivalent influenza vaccines contain two influenza A viruses and one influenza B virus, which have been offered to individuals in Ireland who are 65 years of age or older, those with long-term medical conditions, healthcare professionals and pregnant women. The trivalent vaccine used in Ireland during the 2018/19 influenza season is the most widely used influenza vaccine in Europe. It also provides good protection against the influenza A strain viruses that are circulating this season as most hospitalisations are associated with influenza A. It is expected that approximately one million people in Ireland will have received the trivalent vaccine during the 2018/19 influenza season.
The HSE reviews and updates its influenza plans, including the communications strategy, taking into account lessons learned from previous years, with a view to targeting key groups to create the greatest impact in terms of people receiving the influenza vaccine.
The WHO announced on 21 February 2019 its recommendation for the composition of influenza virus vaccines for use in the 2019/20 northern hemisphere influenza season for the quadrivalent vaccine. The WHO recommends that egg based quadrivalent vaccines for use in the 2019/20 northern hemisphere influenza season contain the following virus strains:
- an A/Brisbane/02/2018 (H1N1)pdm09-like virus;
- an A/Kansas/14/2017 (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).
* The A(H3N2) component was recommended by the WHO on 21 March 2019.
The HSE National Immunisation Office and HSE Procurement are responsible for the purchase of influenza vaccines each year. To ensure adequate vaccine supply, a tender process must be completed 9 months in advance of the first delivery into Ireland (which occurs at the end of August). The procurement process for the 2019/20 influenza vaccine season has already taken place with a decision to purchase the quadrivalent influenza vaccine only for the 2019/20 season. The effect of this decision is that all persons requiring influenza vaccines in 2019/20 will receive the quadrivalent vaccine. Quadrivalent vaccines include a 2nd influenza B virus in addition to the 2 influenza A viruses found in trivalent vaccines. The provision of a quadrivalent vaccine during the next influenza season will offer a substantially greater level of protection to the population when compared to the trivalent vaccine provided in recent years.