In a rare occurrence, composition of this season’s vaccine was postponed in order to give experts more time to monitor circulating influenza viruses. According to WHO, Influenza A(H3N2) viruses change frequentlyii, which makes it challenging to generate candidate vaccine viruses.
To prepare for this season, the FDA and WHO have selected new Influenza A strains for both the trivalent and quadrivalent vaccinesiii:
- Influenza A: A/Kansas/14/2017 (H3N2)-like virus
- Influenza A: A/Brisbane/02/2018 (H1N1)pdm09-like virus
- Influenza B: B/Colorado/06/2017-like (Victoria lineage) virus
The organization also recently launched a new global strategyiv that aims to reduce the burden of seasonal influenza and mitigate the impact of pandemic influenza through stronger surveillance and better tools to prevent, detect, control, and treat flu.