Moderna unveils first clinical data on bivalent COVID variant booster

Moderna has reported preliminary clinical results with a bivalent version of its COVID-19 vaccine that combines its original version with another targeting the Beta variant, and seems to offer improved protection.

The booster shot – called mRNA-1273.211 – offered better and longer-lasting protection compared to the original SpikeVax shot against all SARS-CoV-2 variants, including the prevailing Omicron strain.

The biotech also says it is also testing another version of the mRNA-based vaccine directed more closely at Omicron that could perform even better, with clinical data on that expected within the next few weeks.

"We believe that these results validate our bivalent strategy, which we announced and began pursuing in February 2021," said Stéphane Bancel, Moderna's chief executive.

He stressed however that the mRNA-1273.214 candidate – which combines the current SpikeVax booster with an Omicron-specific candidate – is the company's lead candidate for booster campaigns that may take place in northern hemisphere countries this autumn, if governments decide they are needed.

"We believe that a bivalent booster vaccine, if authorised, would create a new tool as we continue to respond to emerging variants," added Bancel.

The phase 1/2 study involved 895 subjects who received mRNA-1273.211 as a first booster at a dose of either 50 µg or 100 µg around nine to 10 months after the first two SpikeVax doses. Approximately 300 received the 50 µg dose, which was more tolerable and likely to be the one taken forward.

Neutralising antibody titres against Omicron were doubled with the mRNA-1273.211 booster dose compared to the original SpikeVax booster at one and six months, according to the data.

Prof Penny Ward, visiting professor in pharmaceutical medicine at King's College London, said it was encouraging to see data supporting the idea that a mix of vaccines achieves a superior immunological effect than a booster with the same primary vaccine.

"Perhaps unsurprisingly, the short-term immune response against multiple virus variants is better when using the variant booster than the same variant booster, and there is a measure of sustained response over a six-month period post-booster, albeit a reduction in absolute antibody level compared to one month post booster," she commented.

"These data tend to support the conclusion that the time has come to use variant vaccines to boost response among the already vaccinated population, particularly with a view to increasing the breadth of protection against a greater range of variants."

Ward said it would be good to see data from studies of other variant vaccine boosters to compare to the Moderna combination.

Expert advisors "must already be thinking about the population at risk and the vaccines which will be needed to reduce the need for hospitalisation due to COVID and to influenza during the winter months," she suggested.

The European Centre for Disease Prevention and Control (ECDC) and EMA’s COVID-19 task force (ETF) said earlier this month that it is too early to consider widespread use of a second COVID-19 vaccine booster dose in the EU.