Australia is heading for its third Omicron wave in the coming weeks, as BA.4 and BA.5 become the dominant COVID-19 strains.

BA.4 and BA.5 are more infectious than previous COVID-19 variants and subvariants and are better able to evade immunity from vaccines and previous infections. So we’re likely to see a rise in case numbers.

So what are BA.4 and BA.5? And what can we expect in this next phase of the pandemic?

Omicron started off as three subvariants (that is, a group of viruses from the same parent virus), all appearing in late November 2021 in South Africa: BA.1, BA.2, and BA.3.