About the seasonal influenza vaccine 2018/2019
The seasonal influenza vaccine usually consists of three influenza viruses: one type A subtype H1N1 strain, one type A subtype H3N2 strain, and one type B strain. The vaccine is unusual among other vaccines because it must adapt to rapid virus evolution and therefore changes from year to year.
For many years, the trivalent inactivated influenza vaccine (TIV) has been the only alternative for seasonal influenza. TIV is an inactivated (non-live) injectable vaccine that contains virus fragments or purified virus components of each influenza strain. Lower age limit for TIV vaccines are 6 months. There are no upper age limit.
In autumn 2013, a new influenza vaccine which is administered as a nasal spray became available in Norway. This live, attenuated influenza vaccine (LAIV) contains viruses that are cold-adapted and temperature sensitive so they cannot cause influenza illness. The vaccine is quadrivalent (two influenza A strains and two influenza B strains). LAIV should not be given to children younger than two years or older than 17 years of age. Since the vaccine contains live viruses, it should not be given to pregnant girls or children or adolescents who are clinically immunodeficient.
Composition of the seasonal vaccine
The World Health Organization (WHO) has established a network of national influenza centres that monitor influenza activity and recommend the composition of next season's vaccine.
- Recommended composition of influenza virus vaccines for use in the 2018-19 northern hemisphere influenza season
For the season 2018/2019, the influenza vaccine for the Northern Hemisphere contains the following three 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)
The quadrivalent vaccine (LAIV) also contains a B/Phuket/3073/2013-like virus(B/Yamagata/16/88 lineage).
Since the 2009 pandemic, influenza A (H1N1) has been included in the seasonal influenza vaccine. There are no separate vaccines against influenza A (H1N1).