Harvard epidemiologist Dr Eric Liang Feigl-Ding said scientists were monitoring a new variant detected in South Africa, C.1.2, and what it meant for future mutations.
"It's got lots of troubling mutations and it's the most mutative of all variants," Dr Feigl-Ding told Today.
"It's the most genetically distant from the Wuhan 1.0 virus. Whether or not that is the next big thing, it's not necessarily that, it's the fact that the virus is mutating so much faster than we expected.
"In means (for) future variants – Wuhan 1.0 vaccines need to be updated much faster.
"Unless you're triple vaxxed you're not considered fully vaxxed."
Dr Feigl-Ding was one of the first epidemiologists to raise the alarm that COVID-19 was heading towards a pandemic in January 2020.
But he said vaccines are "not a silver bullet", particularly with the Delta strain.
"You must have high filtration masks, you must have ventilation and air disinfection and you must have testing and contact tracing – and fast versions of them," Dr Feigl-Ding said.
He also said he is "not a fan of lockdowns" as a way of containing the virus.
"They are necessary as a last resort. No-one wants lockdowns," he said.
Dr Feigl-Ding said methods like ensuring school children had their lunches outside, office buildings installing HEPA filters and upper room UV for all indoor spaces were all necessary – along with vaccine mandates.
"If you avoid these things, you're headed for a lockdown. You have to do everything else in the middle not just vaccines."