WHO: Early signs show Omicron has 'growth advantage' over Delta variant

The WHO also said the limited data available so far makes it “challenging to assess” whether this variant could make people more ill than with other variants. 

However, the agency warned even if the severity remains the same as for Delta or is potentially lower, the growth advantage could ultimately mean more cases.

In an update on the new variant, the WHO warned that "it is expected that hospitalisations will increase if more people become infected and that there will be a time lag between an increase in the incidence of cases and an increase in the incidence of deaths.” 

Examining the risk of re-infection, the WHO said early analysis suggests that the mutations or changes in Omicron may neutralise the antibodies which emerge after infection, meaning the natural immunity which people have post-infection may not be as effective against the new variant as against previous ones.

They said this could be one reason why Omicron is spreading so quickly in South Africa where many people had the virus already, which up until now was seen as offering medium-term protection against re-infection.

In contrast to European countries, the vaccination rate remains low at just 35% of adults, the WHO said, so it is difficult to say yet what the effect of vaccination is on this variant. The variant was first identified in South Africa, although the WHO said: “hundreds of cases” have now been found elsewhere.

Just one case has been reported in Ireland - identified in Co Meath — and three cases have been reported in Northern Ireland. The Delta variant is still driving the vast majority of Irish infections.

The WHO refrained from commenting on transmissibility for now, saying again it is too early.

“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,” they said.

The update notes a scenario laid out by the European Centre for Disease Prevention and Control estimating if Omicron reaches 1% of cases it would become dominant in Europe by January.

The variant is being identified in Ireland and elsewhere by using a tool called “s gene target failure” on PCR tests positive for the virus.

The “s gene” is a part of the virus which is not part of the Omicron variant so when that does not appear in the results then scientists can say this person likely has Omicron. It gives a faster indication so the spread of the variant can be more easily tracked.

The PCR results are then re-tested using whole-genome sequencing to give further confirmation.