States should reconsider their responses to Covid-19 and speed up vaccination programs to cope with the Omicron strain, although it is too early to say how much existing vaccines will protect against the new variant, the World Health Organization said today.

The global spread of the Omicron variant suggests it could have a major impact on the Covid-19 pandemic and should be prevented before more patients are hospitalized, said World Health Organization (WHO) Director-General Tedros Adanom Gebrejesus.

- We call on all countries to increase surveillance, testing and sequencing. "Every self-proof now costs lives," he told a news conference in Geneva.

The WHO has commented on the findings of Pfizer and Biontec on the effectiveness of their Omicron strain vaccine, after pharmaceutical companies said that their three doses of coronavirus vaccine in a laboratory test showed a neutralizing effect against the Omicron strain, and that two doses produced neutralizing antibodies.

Warning of hasty conclusions from the trials, WHO chief scientist Sumia Swaminathan said it was to say early on whether a reduction in neutralizing antibodies means the vaccine is less effective.

"We do not know that," Swaminathan said, adding that a coordinated global research effort was needed.

The WHO has also announced that it will publish a review of its position on booster doses in a few days, but with alarmingly low vaccination rates in much of the developing world, the use of primary doses instead of boosters remains a priority.