The Omicron variant of Covid-19 has now been reported in 57 countries and continues to spread rapidly in South Africa, the World Health Organization (WHO) says.
But the latest epidemiological report from WHO says given the Delta variant remains dominant, particularly in Europe and the US, it is still too early to draw any conclusions about the global impact of Omicron.
The European Centre for Disease Prevention and Control has predicted that the Omicron variant could become the dominant variant in Europe within months.
For now, though, the Delta variant continues to dominate cases, and more data is needed to determine Omicron’s infectiousness and severity, WHO says.
“While there seems to be evidence that the Omicron variant may have a growth advantage over other circulating variants, it is unknown whether this will translate into increased transmissibility,” the WHO report said.
Of 899,935 Covid-19 test samples sequenced and uploaded to the global Covid database in the last 60 days, 897,886 (99.8%) were confirmed to be Delta, while 713 (0.1%) were Omicron.
The WHO report said South Africa reported 62,021 cases of the variant between 29 November and 5 December – an 111% rise from the previous week.
The country also had an 82% increase in hospital admissions due to Covid-19 during the week to 4 December – 912 admissions compared with 502 the week prior. But it is not yet known how many of these cases were due to Omicron.
Omicron seems to be spreading rapidly in South Africa despite high rates of past infection with Covid. Estimates suggest between 60% and 80% of the population have previously been infected. Vaccination rates are low, at about 35%.
Data is still too limited to know with certainty whether Omicron changes the severity of the illness. As of 6 December, all 212 confirmed Omicron cases across 18 European Union countries were classed as asymptomatic or mild.
But WHO said “even if the severity is equal or potentially even lower than for Delta variant, it is expected that hospitalisations will increase if more people become infected”.
“Further information is needed to fully understand the clinical picture of those infected with the Omicron variant,” the report said.
WHO said that preliminary data suggests the mutations in the Omicron variant may reduce the ability of natural immunity to protect against reinfection after infection with the virus.
Omicron carries mutations which may reduce the ability of the antibodies resulting from natural immunity to protect against the virus, but further studies are needed to confirm its ability to reinfect previously confirmed cases or vaccinated people.
The report concluded many questions about the Omicron variant remain unanswered, but that more information will emerge in the coming weeks.
Pharmaceutical company Pfizer this week reported results from preliminary studies that suggested two doses of its Covid-19 vaccine have a significantly reduced ability to neutralise the Omicron variant, and that three doses may be needed.
A small study from South Africa, which is not yet peer reviewed, also suggested that antibody neutralisation is reduced about 40-fold against Omicron compared to the original virus.
Dr Deborah Cromer, a senior research fellow at the University of NSW’s Kirby Institute, said in the past day “a swathe of preliminary data has emerged showing the drop in immunity against the Omicron variant”.
She said this data has come from studies looking at blood from people who have recovered from Covid-19 and/or have been vaccinated against the disease.
“All studies show less immunity against Omicron than against the original virus strain, however the reported drops vary widely,” she said.
“The estimates we have seen to date of people’s immunity against Omicron range from half to one-fortieth of the immunity present against the original strain.
“Regardless of the number, it is clear that increased levels of immunity will be required to provide protection against Omicron, and therefore booster shots are now more important than ever to help achieve this.”
The first known laboratory-confirmed case of Omicron was identified from a specimen collected on 9 November in South Africa, with the variant reported to WHO on 24 November.