Makers of Covid-19 vaccines should gear up for the “likelihood” of needing to adjust their products to protect against the Omicron variant, the World Health Organisation's (WHO) has spokesperson has said, according to Reuters.

Christian Lindmeier, speaking at a UN briefing in Geneva, said the agency was still studying the transmissibility and severity of the new variant, first reported in Southern Africa.

“It is very recommendable that vaccine manufacturers already start planning ahead and plan for the likelihood for having to adjust the existing vaccine,” he said. “That's good not just to wait until the final alarm bell rings.”

Doctors in South Africa has there had been a spike in hospitalisations among young children after Omicron swept through the country but stressed it was early to know if they were particularly susceptible, AFP reports.

The first cluster of cases centred around university students, and then spread quickly among young people who seem to have spread it to older people.

But scientists and health officials said they had seen increasing hospital admissions in children under five, along with higher positivity rates among children aged 10-14.

Covid-19 vaccines made by Pfizer and Moderna that use mRNA technology provide the biggest boost to antibody levels when given 10-12 weeks after the second dose, Reuters quotes a British study as saying.

The "COV-Boost" study was cited by British officials when they announced that Pfizer and Moderna were preferred for use in the country's booster campaign, but the data has only been made publicly available now.

The study found that six out of the seven boosters examined enhanced immunity after initial vaccination with Pfizer-BioNTech's vaccine, while all seven increased immunity when given after two doses of AstraZeneca's vaccine.

Read more from Reuters here

India's health ministry has said that the severity of the Covid-19 disease from the Omicron variant in the country could be low because of vaccination and high exposure to the Delta variant, Reuters reports.

"Given the fast pace of vaccination in India and high exposure to Delta variant as evidenced by high seropositivity, the severity of the disease is anticipated to be low," it said in a statement. "However, scientific evidence is still evolving."

The Omicron variant of Covid-19, which had been undetected in the US before the middle of this week, has been discovered in at least five states, showing yet again how mutations of the virus can circumnavigate the globe with speed and ease.

Just a day after the first known US case was found in California, tests showed the Omicron variant had infected at least five people in the New York City metropolitan area, plus a man from Minnesota who had attended an anime convention in Manhattan in late November.

Health officials in each state said there was no cause for undue alarm. But the spread of the cases, some involving people who hadn’t been away from home recently, meant the variant was likely already circulating domestically in some parts of the US.

Read more from AP here.