New hope for Covid vaccine may delay rollout of fourth shots

Despite closely related variants of the dominant Omicron strain known as BA.4 and BA.5 taking hold across Australia, progress on top-up vaccines could prompt health authorities to delay the rollout of a fourth shot.

Health authorities could be prompted to delay the rollout of a fourth Covid shot while awaiting the availability of targeted vaccines. Picture: Supplied

Progress on top-up vaccines against virulent Covid-19 subtypes could prompt health authorities to delay the rollout of a fourth shot, despite a national spike in case numbers.

Victorian Premier Daniel Andrews, a vocal advocate of mandating the additional booster for healthcare workers, changed his tune on Sunday, conceding the fourth dose might better wait until targeted vaccines were available.

“There’s this real dilemma at the moment,” he said. “Do we maybe go to a fourth dose for our health workers – which is something I’ve pushed for, something I’ve spoken to the PM about – or maybe do we wait a little while because there might be an even better vaccine that’s even more effective?”

Closely related variants of the dominant Omicron strain known as BA. 4 and BA. 5 are fast taking hold in Australia, heightening pressure on a hospital system being slammed by a resurgence of seasonal influenza. US drugmaker Pfizer, supplier of one of the four Covid vaccines available in this country, announced at the weekend that a modified ­version of its mRNA shot had boosted antibody levels against the new Omicron subtypes in laboratory trials.

Moderna, whose Covid shot is also available here, has made similar progress while rival big pharma outfits Sanofi and Glaxo­SmithKline say their latest vaccines target BA.4/BA.5 mutations.

Moderna announced this month positive results for a new vaccine that targets both the original Covid strain and Omicron. Picture: Frederic J. Brown/AFP

These are on the cusp of overtaking Omicron BA.2 and now account for more than a third of new infections in NSW, driving a big jump in cases nationwide because of the altered virus’s ability to evade existing vaccines.

Former chair of the federal government’s vaccine adviser Allen Cheng said the expert panel was closely following developments in the US.“One of the big considerations we are looking at is, do we recommend the fourth dose more broadly in Australia, knowing that there might be a better fourth dose to get down the line?” said Professor Cheng, who is a voting member of the Australian Technical Advisory Group on Immunisation.

While ATAGI has no immediate changes to the advice on fourth doses, “the alternative is that maybe there will be a better variant vaccine and if we just wait a few months longer, we will have access to that,” he said at the weekend.

A fourth dose is available to anyone aged over 65, Aboriginal and Torres Strait Islanders over 50 and Australians under 64 who are immunocompromised.

In the US, the Food and Drug Administration is assessing the rejigged Covid vaccines by Moderna and Pfizer in the hope that modified boosters could better protect the population.

Pfizer and its partner BioNTech studied targeting just Omicron or a combination booster that added the Omicron protection to the original vaccine. They also tested whether to double the strength of existing doses.

Pfizer said both approaches promoted a sizeable increase in Omicron-fighting antibodies.

Nearly a third of Australians have caught Covid, with new infections topping 23,000 a day.