Fact Check-No evidence COVID-19 Omicron XBB variant has higher mortality rate, or is five times more ‘toxic,’ than Delta

Social media users in Singapore are copy-pasting a text post which warns that the COVID-19 Omicron XBB variant, first discovered in August, is five times more “toxic” and has a higher mortality rate than the Delta variant. However, there is no evidence to support this, according to Singapore’s Ministry of Health. Likewise, the World Health Organisation (WHO) says current data does not suggest XBB is more deadly than Omicron, which itself is less lethal than Delta.

The 300-word post can be seen in an example on Facebook (here), where it claims: “Of course, the COVID-Omicron XBB is 5 times more toxic than the Delta variant and has a higher mortality rate than the Delta.”

The rest of the post does not fall within the scope of this fact check.

Other iterations can be seen on Facebook here, here and here.

XBB, a hybrid between two descendants of the BA.2 version of Omicron (here), has led to a surge in hospitalizations in Singapore, Reuters reported on Oct. 25 (here). There is so far no evidence of significant differences in its virulence compared with its 'parent' lineage (here).

However, the University of Washington's Institute for Health Metrics and Evaluation (IHME), said that while early analysis suggests the variant is more transmissible than earlier versions of Omicron, it also appears to cause less severe disease (here).

Since their emergence, the Omicron lineages have been notable for their high immune evasion, which helps them transmit and reinfect people more readily, and their lower disease severity as compared with the previous 'variant of concern' Delta (here).

When contacted in November about the XBB claim on social media, Singapore’s Ministry of Health (MoH) directed Reuters to three articles it published on Oct. 11, 14 and 15, which also said there had been no evidence of XBB causing more severe illness (here, here and here).

A World Health Organisation press release on XBB states (here) : “While further studies are needed, the current data do not suggest there are substantial differences in disease severity for XBB infections. There is, however, early evidence pointing at a higher reinfection risk, as compared to other circulating Omicron sublineages.”


False. There is no evidence the SARS-CoV-2 Omicron XBB variant is more deadly or causes more severe COVID-19 than the Delta variant.

This article was produced by the Reuters Fact Check team. Read more about our fact-checking work here.