RIVM examined test samples from 70,000 people aged 12 years and older who tested positive for the coronavirus in recent weeks (22 November-19 December 2021). The Omicron variant was found in 931 of these people. Of these people who tested positive and had the Omicron variant, 84.7% had been fully vaccinated. Looking at people who tested positive and had the Delta variant, only 62% had been fully vaccinated. This shows that vaccination offers less effective protection against the Omicron variant than against the Delta variant. 2.8% of people who tested positive and had the Omicron variant had previously had a coronavirus infection, compared to 1.3% of those who had the Delta variant.   This means that people who have already had COVID-19 are more likely to be reinfected if they are exposed to the Omicron variant. 

The number of Omicron samples found in this study are still limited. RIVM will keep researching the Omicron variant. For example, this study could not determine whether there are differences between the Omicron variant and the Delta variant in terms of the risk of serious illness. More will become clear in the next few weeks, as the new variant increases rapidly.