Two shots of Pfizer's Covid vaccine offers around 70 percent protection against severe disease from Omicron, according to results of a study published Tuesday in South Africa.
The emergence of the highly mutated variant, first detected in South Africa last month, sparked fears that it could cause severe disease, be more contagious or could evade vaccines.
Early indicators suggest that it could be more transmissible, but promising data so far has suggested that vaccines still offer protection against Omicron.
The latest research out of South Africa suggested that two doses of the Pfizer/BioNTech vaccine still offered protection against serious illness.
"The double dose of Pfizer/BioNTech vaccine showing 70 percent effectiveness in reducing risk of hospitalisation," said Ryan Noach, the head of South Africa's leading private health insurance company, Discovery, which co-led the study.
Two doses of the vaccine offered 93 percent protection against earlier variants, according to the companies.
The study was based on the results of 78,000 PCR tests taken in South Africa between November 15 and December 7 and was conducted by Discovery along with the South African Medical Research Council (SAMRC).
"We are extremely encouraged by the results," said SAMRC head Glenda Gray.
But Noach warned that despite the protection offered by two doses, hospitals could still be overrun since Omicron is spreading rapidly in South Africa.
Last week, South Africa approved booster shots for all citizens over 18 as it seeks to stem the rise of new infections.
So far more than 17 million people have been vaccinated in South Africa, or around a third of the country's population.
The government had initially wanted to vaccinate around 70 percent of the population by year's end, but has moved that target to March 2022.
Pfizer/BioNTech has previously said that two shots may not be enough to protect against catching Omicron, though they appeared to be effective against severe disease.
In a preliminary study published last week the companies said a third shot appeared to be effective against the strain.