San Francisco Frontiers - Moderna says new booster candidate effective against Omicron subvariants

The US biotech company announced earlier this month that the so-called "bivalent" vaccine, which targets the original Covid strain and original Omicron BA.1, performed better against both compared to its original Covid vaccine called Spikevax.

In new results from a clinical study, the company said that the booster also did well against BA.4 and BA.5, Omicron's latest subvariants that are becoming dominant thanks to their increased ability to evade prior immunity, and enhanced transmissibility.

The bivalent booster elicited high levels of infection-blocking antibodies against BA.4 and BA.5 both in people who were previously infected and those not previously infected.

However even those high levels were still one third the levels achieved against the original Omicron strain, BA.1

"We will submit these data to regulators urgently and are preparing to supply our next generation bivalent booster starting in August, ahead of a potential rise in SARS-CoV-2 infections due to Omicron subvariants in the early fall," said Moderna CEO Stephane Bancel in a statement.

The BA.4 and BA.5 variants hammered South Africa, where they were first discovered, in April and May -- despite high population immunity conferred by prior waves and vaccinations.

Like other Omicron variants they tend to have a milder disease course as they settle less in the lungs and more in the upper nasal passages, causing symptoms like fever, tiredness and loss of smell.

Y.Harris--SFF