The World Health Organization (WHO) has warned that the recently discovered COVID-19 Omicron variant poses a "very high" global risk due to the speed of its transmission and the higher risk of reinfections. In technical advice issued to its member states on 29 November, the agency flagged out two areas that it says governments need to prioritise: vaccinating vulnerable groups and bolstering essential health services.

"Increasing cases, regardless of a change in severity, may pose overwhelming demands on health care systems and may lead to increased morbidity and mortality. The impact on vulnerable populations would be substantial, particularly in countries with low vaccination coverage," the advisory stated.

The WHO's warning comes right after reports from South Africa indicated that Omicron infections are not severe in vaccinated individuals. Dr. Angelique Coetzee, chair of the South African Medical Association, has described the symptoms as "extremely mild", with patients reporting fatigue and body aches but none of the respiratory impairment or characteristic loss of smell and taste associated with other strains of COVID infections.

Nevertheless, the WHO is taking the high transmissibility of the variant seriously, and so are many countries. Although the WHO had earlier urged governments not to take knee-jerk reactions, multiple countries have banned travellers from South Africa and its neighbouring countries since Omicron infections were first reported last week. Japan, Israel, and Morocco have put the strictest border controls in place - the three countries have banned all foreign travellers. Some countries, like Australia, have delayed their border relaxation measures.

South Africa President Cyril Ramaphosa has hit back at the bans on travellers, calling them unjustified, unscientific, and harmful to the recovering economies of the affected countries.

“The only thing the prohibition on travel will do is to further damage the economies of the affected countries and undermine their ability to respond to, and recover from, the pandemic,” he said in an address on 28 November.

Dr. Matshidiso Moeti, the WHO Regional Director for Africa, also said: "With the Omicron variant now detected in several regions of the world, putting in place travel bans that target Africa attacks global solidarity."