Moderna starts dosing patients with its Omicron COVID jab

Moderna has started human trials of an Omicron version of its COVID-19 vaccine SpikeVax, just in case a modified version will be needed to boost protection against the new variant later this year.

The biotech has also reported new data suggesting that may well be the case, with a six-fold reduction in neutralising antibody levels against the variant six months after a third dose of the current SpikeVax shot.

That is a much steeper decline than the 2.3-fold reduction seen with the original strain of SARS-Cov-2 over the same time period, according to Moderna, although it said antibody levels were still detectable in the study, which has been published in the New England Journal of Medicine.

Seven months after a second dose and before the third booster dose, Omicron neutralisation was detected in only 55% of participants, according to the researchers. It's not clear yet how that will affect the risk of severe disease with the new variant.

The start of the phase 2 study of the Omicron version of the vaccine comes just a few days after fellow mRNA vaccine developers Pfizer and BioNTech began dosing patients with a modified Comirnaty shot also directed against Omicron, now firmly established as the dominant strain circulating worldwide.

Moderna's 600-patient study will include two patient cohorts, one involving people who have received two doses of SpikeVax (mRNA-1273) and second who have been given three doses, with a single dose of the Omicron version (mRNA-1273.529) given as a booster.

Pfizer and BioNTech is taking a slightly different approach too its 1,420-subject study with three cohorts, one of which will include an entire three-dose course of the Omicron jab.

"We are reassured by the antibody persistence against Omicron at six months after the currently authorized 50 μg booster of mRNA-1273," said Moderna chief executive Stéphane Bancel.

"Nonetheless, given the long-term threat demonstrated by Omicron's immune escape, we are advancing our Omicron-specific variant vaccine booster candidate [and] evaluating whether to include this Omicron-specific candidate in our multivalent booster programme."

The company recently said it has two multivalent booster candidates in the clinic that are designed to anticipate mutations in SARS-CoV-2.

Omicron accounts for 99.9% of all US COVID-19 infections, according to Centres for Disease Control and Prevention data published on Tuesday, with the Delta variant making up the remaining 0.1%.