Maria Van Kerkhove, WHO technical lead on Covid-19, said there was evidence now to suggest the strain, which has pushed India's daily Covid-19 infections beyond 400,000 in recent days, is more infectious than others.
"I am concerned about 617 - I think we have to keep a very close eye on it", said Kristian Andersen, a virologist at Scripps Research Institute in La Jolla, California.
The statement from Ofrin came a day after the World Health Organization classified the B.1.617 variant, or the "double mutant" strain as a variant of global concern. The UK Prime Minister revealed there are now "860 or so" cases in England of the VOC detected in India, "but there may be more" as the variant "may be considerably more transmissible".
WHO director-general Tedros Adhanom Ghebreyesus said the WHO Foundation was launching a "Together for India" appeal to raise funds to purchase oxygen, medicines and protective equipment for health workers.
The BBC reports, "However, early lab results and real-life data suggest the Pfizer vaccine can protect against the new variants, although slightly less effectively".
More details would be provided about the variant in the WHO's weekly epidemiological update on Tuesday, Van Kerkhove said.
Separately, the health ministry reported on Tuesday 4,734 new coronavirus infections, the lowest single-day tally since March 17, bringing total cases to more than 1.11 million. The virus has utterly overwhelmed India's health system and experts say the actual numbers are likely far higher.
They are seen as more risky than the original version of the virus by either being more transmissible, deadly or able to get past some vaccine protections.
Other variants of concern include B.1.1.7, which was first identified in the United Kingdom, and P.1, which was originally detected in Brazil.
Even if vaccine efficacy may be diminished against some variants of Covid-19, the jabs can still provide protection against serious illness and death.
The WHO explained Wednesday that B.1.617 was added to the list because it appears to be transmitting more easily than the original virus, pointing to the "rapid increases in prevalence in multiple countries".
The WHO's chief scientist Soumya Swaminathan agreed, urging a "balanced approach".
Experts highlight that the more the virus spreads, the bigger the risk it will find ideal conditions to mutate in concerning ways, stressing that everything must be done to rein in transmission.
However, countries must continue to be vigilent to limit the spread of variants, because "we will continue to see variants emerge", said Van Kerkhove.