On 28 November, the World Health Organization designated the variant B.1.1.529 a variant of concern, naming it Omicron. By February 2022, it overtook the Delta variant to become the dominant strain circulating in Australia and worldwide.
Since then subvariants of Omicron have emerged, the key ones being BA.1, BA.2, BA.4, and BA.5. Both BA.5 and, to a lesser extent, BA.4, rapidly replaced other Omicron subvariants and are now dominant in Australia and worldwide, causing concerning spikes in hospitalisations and deaths.
