South Africa has approved the use of Pfizer's coronavirus booster vaccine for people aged over 18 years, amid mounting concern following a record of almost 20,000 infections overnight, largely ascribed to the new and highly-mutating Omicron variant.

The South African Health Products Authority (SAHPRA) on Wednesday approved the use of Pfizer's Comirnaty COVID-19 vaccine after BioNTech and Pfizer announced that two doses of their vaccine may not be enough to protect against the Omicron variant.

It said a third dose of the vaccine could be administered to those over 18 years at least six months after their second jab, or 28 days after the second jab for those over 12 years who are severely immune-compromised.

The decision by SAHPRA came after South Africa recorded a new high of 19,842 infections overnight. The death toll has now also surpassed the 90,000-mark with 36 new deaths.

More than 60 per cent of these infections were in Gauteng province, the economic hub of the country, as speculation grew over a more severe lockdown being imminent. South Africa is currently at the lowest Level One of its five-level lockdown strategy.

President Cyril Ramaphosa was expected to hold urgent meetings with the Corona Command Council and his Cabinet immediately upon his return from a week-long visit to four West African nations Thursday.

There is a growing fear that the infection figures will continue to rise exponentially in other provinces also as holiday-makers head to the coastal provinces and workers from Gauteng visit their traditional family homes for gatherings over the festive season.

Despite repeated calls by the government, unions and business leaders, vaccine hesitancy continued unabated over the past week as infections reached staggering numbers.

On Monday, Health Minister Joe Phaahla expressed concern over hospitals beginning to fill up with COVID-19 cases, although the majority of cases were not severe.

Phaahla also shared concern over children and expectant mothers when he spoke at the opening ceremony of the International Conference on AIDS and STIs in Africa in Durban.

"We are seeing babies, toddlers and pregnant women in hospital on oxygen. The message is clear, we need to be more vigilant than ever," the minister cautioned.

On Tuesday, Jacques van Zuydam, the Department of Social Development's chief director for population and development, disclosed that South Africa's life expectancy had gone down by three-and-a-half years because of the pandemic.

He was speaking at a BRICS webinar on the demographic impact of the pandemic.

"There was a significant rise in deaths in 2021, approximately by 34 per cent from the previous years," he said, adding that what had not been expected was the impact that the pandemic had on mental health.

"There has been a reported rise in mental illness associated with increased social isolation, disruptions in daily life routines and pressures associated with the loss of livelihoods, he added.