Moderna is the first vaccine maker to announce a trial for a booster against a new variant © Reuters

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Moderna is launching a trial of a new Covid-19 vaccine to tackle the coronavirus strain that has emerged in South Africa after warning that its existing jab was less effective at tackling the new variant.

Laboratory tests show Moderna’s Covid-19 vaccine still works against the variant named 501.V2, which first emerged in South Africa, and B.1.1.7, which was first discovered in the UK, the company said.

But it warned that its shot produced only one-sixth of the antibodies in response to the South Africa variant than for the original virus. This has raised concerns that the immunity to the new strain offered by the company’s original jab may wane significantly — particularly in older people.

Stéphane Bancel, Moderna chief executive, said the company was preparing for a “worst-case scenario”, even though he had “zero concerns” about the vaccine’s efficacy in the coming months. 

“If something needs to be done in the summer, we'll do something, but we cannot be late,” he told the Financial Times. “We don’t want the virus to win, we want the human race to win.” 

Moderna is one of the leading makers of coronavirus vaccines, alongside rivals from BioNTech/Pfizer and Oxford university/AstraZeneca. Its vaccine is being used in the US, which bought 200m doses and funded the company with up to $4.1bn, while the EU has ordered 160m doses.

The UK has ordered 17m doses, which are due to start arriving in the spring. 

Merck, one of the world’s leading vaccine makers, is ending its Covid-19 vaccine development after its two candidates failed to elicit immune responses as strong as those created by shots that are already available.

The European Commission has piled pressure on AstraZeneca over its planned cut to first-quarter vaccine dose deliveries to the EU. AstraZeneca has said there is no “scheduled delay” to shipments of its vaccines, but warned that “initial volumes” would be lower than anticipated because of reduced yields at a manufacturing site in the EU supply chain.

Emergency talks between the two sides were due to take place on Monday night. Stella Kyriakides, the EU’s health commissioner, said AstraZeneca’s proposed new supply schedule was “not acceptable”, adding that the company’s explanations for the problems had “not been satisfactory”.

New variants pose a potential problem to pharma companies that have developed vaccines. Moderna hopes that, by preparing for a potential booster shot now, it will be ready by the autumn if needed.

Its messenger RNA technology can be quickly adapted for new variants. If needed, the booster would be given to people who had already received the Moderna vaccine.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said other vaccine makers may also want to act to “stay ahead of the game”.

“We believe it is prudent to do to at least get a start,” he told the Financial Times. “You may not have to utilise that, but rather than just waiting until all of a sudden you find out that you have a variant that is dominant that you need to make a response against because the vaccine is not adequate.”

He added that he “very seriously doubts” if a large multi-thousand person trial will be necessary to authorise a booster.

Shares in Moderna added 4.3 per cent to $136.70 in pre-market trading in New York.

Johnson & Johnson, which has conducted some of the trials for its vaccine candidate in South Africa, is expected to release its phase-3 data this week. That should give another clue, as it could compare the prevalence of disease with trial participants in the US.

The BioNTech/Pfizer vaccine also works against the UK-discovered B.1.1.7 but has not announced test results against the variant that emerged in South Africa. 

Moderna is working with the US National Institutes of Health on the trials. Mr Bancel said a few thousand trial participants would be given a booster shot, divided into two groups: one to receive the original vaccine again, and another to get a new vaccine formulated to target 501.V2. The trial will also test to see what dose is needed for a booster. 

Regulators may be able to approve a new vaccine just based on a “bridging study”, which examines participants’ antibodies to the new variant after taking a booster, rather than a lengthy phase-3 trial, which counts how many develop Covid-19 in each trial arm. 

A group of scientists in South Africa said this month that vaccines could be less effective against the 501.V2 strain, because it has an extra mutation in a key part of the spike protein that the virus uses to enter human cells.

Additional reporting by Clive Cookson and Anna Gross in London and Michael Peel in Brussels

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