Health authorities have warned of a new wave of Covid-19 cases and hospitalisations being driven by Omicron subvariants XBB and BQ.1. The latest federal health department data shows that as of 25 October, the average national daily cases increased by 2.2% compared with the previous week.
So how worried should we be about these variants, and do they affect advice around booster doses?
What do we know about the new variants?
Despite driving an increase in cases, the World Health Organization (WHO) says XBB and BQ.1 are not different enough from each other, or from other Omicron lineages, to warrant labelling them new variants of concern.
Variants of concern are those that show increased transmissibility, virulence or change in clinical disease, and a decreased effectiveness of public health and social measures.
XBB and BQ.1 are subvariants of Omicron, which continues to be a variant of concern.
Examining global data available to date, WHO said there is early evidence that there is a higher risk of Covid-19 reinfection from XBB and BQ.1 compared to other circulating Omicron subvariants. However, cases of reinfection appear to be largely occurring in those previously infected with pre-Omicron strains, such as Delta, WHO says.
Keep up to date with your boosters
The Victorian department of health says the ability of XBB and BQ.1 to escape immunity from past infection, combined with waning immunity from past vaccination, are driving rises in cases overseas. It is why remaining up to date with booster shots is critical.
In October, the health minister, Mark Butler, expressed concern that there were still “several million people” who, more than six months since having their second vaccine shot, have not received their third.
Boosters and current antivirals such as Paxlovid appear to work well against the new variants. So while the variants may trigger a new wave of infections, for most people, it appears these infections will not be severe. There is no suggestion that fifth doses will be needed for the general population in light of the new variants.
Does the Omicron-specific booster change anything?
In September, the first bivalent Covid-19 vaccine was approved for use in Australia, targeting two different Covid-19 viruses: the original 2020 strain and Omicron variant BA.1. It is commonly referred to as the Moderna bivalent vaccine, and in Australia it has been available to people aged 18 and over as a third or fourth dose since 10 October.
A second bivalent vaccine, the Pfizer bivalent vaccine, was provisionally approved by drug regulator the TGA in October. But the Australian Technical Advisory Group on Immunisation (Atagi) is yet to advise on how the Pfizer bivalent vaccine should be rolled out and used, and it is not yet available.
However, Atagi advice on boosters has not changed in light of the new variants or the new bivalent vaccines.
Atagi considers receiving all recommended booster doses to be a more important factor than which variant is targeted by those doses. This is because even if the variant targeted by a vaccine does not necessarily “match” the circulating variants, the available vaccines all induce a broad immune response that protects against the circulating variants.
Atagi have made no changes to the current booster recommendations and is not advising any extra booster doses beyond the fourth dose in selected populations. Booster doses should be given at least three months after the most recent Covid-19 vaccine dose or a Covid-19 infection.
Staying up to date with your Covid-19 vaccinations remains the best way to protect yourself against severe illness and death, including with the most recently detected Omicron subvariants.
The latest Covid-19 vaccine advice, including on boosters, can be found on the federal department of health website.
