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The new Covid shot that specifically targets Omicron variant elicits a strong immune response against the strain, widely known to evade vaccines, Pfizer and BioNTech have said.

According to the companies, just a month after administration, a booster dose of the Omicron-adapted monovalent candidates (at 30 and 60 microgram doses) increased neutralising antibodies against Omicron BA.1 to 13.5 and 19.6-fold above pre-booster dose levels.

A booster dose of the Omicron-adapted bivalent candidates conferred a 9.1 and 10.9-fold increase in neutralising antibodies against Omicron BA.1, that was circulating last winter.

Data from the Phase 2/3 trial that included 1,234 people aged 56 or older, showed that both Omicron-adapted vaccine candidates were well-tolerated in participants, the companies said.

"Based on these data, we believe we have two very strong Omicron-adapted candidates that elicit a substantially higher immune response against Omicron than we've seen to date," said Albert Bourla, Chairman and Chief Executive Officer, Pfizer, in a statement.

"Omicron has newly evolving sublineages that have outcompeted BA.1 and exhibit a trend of increasing potential for immune escape. We will therefore remain vigilant and are prepared to rapidly adapt our Omicron-adapted vaccine candidates to emerging sublineages if epidemiological and laboratory data suggest, added Prof. Ugur Sahin, CEO and Co-founder of BioNTech.

Further, the companies noted that their early laboratory studies suggest that both Omicron-modified candidates also neutralise the Omicron BA.4 and BA.5 sub-variants that have been circulating more recently, with approximately 3-fold lower antibodies than BA.1.

The companies stated they are continuing to collect data on how well the boosters perform versus the more recently circulating strains.

The companies will share the results with the US Food and Drug Administration (FDA) and European Medicines Agency (EMA), ahead of the FDA advisory committee meeting on June 28, to discuss whether to update Covid vaccines.

The companies have also submitted additional data from their ongoing Covid-19 booster studies, including data on an additional dose of their current Covid-19 vaccine and Beta candidate, to further demonstrate the flexibility and potential benefit of mRNA-based vaccines.

Meanwhile, rival Moderna has also made a redesigned vaccine targeting the BA.1 Omicron subvariant. The company said its updated vaccine worked well against more recent Omicron subvariants, and that it was moving forward with plans to ask regulators for approval.