A new coronavirus strain, named Mu, is being investigated by the World Health Organisation (WHO).
The WHO has designated the new strain as a "variant of interest".
Mu, or B.1.621, was first identified in Colombia and cases have been recorded in South America and Europe.
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The WHO's weekly bulletin on the pandemic said the variant has mutations suggesting it could be more resistant to vaccines, as was the case with Beta, but that more studies would be needed to examine this further.
It said: "Since its first identification in Colombia in January 2021, there have been a few sporadic reports of cases of the Mu variant and some larger outbreaks have been reported from other countries in South America and in Europe.
"Although the global prevalence of the Mu variant among sequenced cases has declined and is currently below 0.1%, the prevalence in Colombia (39%) and Ecuador (13%) has consistently increased.
"The epidemiology of the Mu variant in South America, particularly with the co-circulation of the Delta variant, will be monitored for changes."
There are currently four coronavirus variants of concern, as deemed by the WHO, with the Alpha variant - first recorded in Kent - seen in 193 countries, Beta in 141, Gamma in 91 and Delta in 170 countries, while Mu is the fifth variant of interest.
The news comes as Downing Street confirmed it intends to press on with plans to introduce vaccine passports for nightclubs from the end of September.
The proposals have previously been met with criticism from politicians on both sides as well as leaders in the night time hospitality industry.
The scheme would see members of the public required to show proof of their vaccine status to gain entry to domestic venues and events.
But on Tuesday the Prime Minister's official spokesman said the Government's plans remained in place.
He said: "We set out broadly our intention to require our vaccination for nightclubs and some other settings and we'll be coming forward in the coming weeks with details for that."
