Covid-19 vaccine manufacturer Moderna says its two-dose jab is effective against new variants of the virus found in the UK and South Africa.

The company said on Monday it would start testing an additional booster dose of the vaccine for the South African strain in order to proactively address the pandemic as the virus continues to evolve.

Pre-clinical trials are due to see if it would be more effective in boosting antibodies against the variant and other future variants. 

Although all viruses mutate constantly, scientists are concerned about the mutations discovered in Britain and South Africa because they are believed to be capable of altering key functions of the virus.

Moderna said a study showed there was “no significant impact” on the vaccine’s effectiveness against the UK strain. There was a six-fold reduction when it came to the South African variant, but the firm said the effectiveness was still “above levels that are expected to be protective”.

Chief executive Stephane Bancel said: “We are encouraged by these new data, which reinforce our confidence that the Moderna Covid-19 vaccine should be protective against these newly-detected variants.”

The UK Government has purchased 17 million doses of the Moderna vaccine – enough to vaccinate 8.5 million people, but the first doses are not expected to arrive in the country until the spring.