As a recent study revealed that the first solid evidence for a Delta and Omicron recombinant virus has been found, the World Health Organisation (WHO) noted that this was expected with both Omicron and Delta variants of COVID circulating widely. WHO also assured that several studies are underway to understand its severity and transmissibility. 
What is Delta+Omicron recombinant virus?

A recent study by the French institution Pasteur Institute found solid evidence for a Delta and Omicron recombinant virus. These data and analysis provide definitive confirmation of an authentic recombinant virus derived from the GK/AY.4 (Delta) + GRA/BA.1 (Omicron) lineages. 

The recombinant virus was identified in several regions of France and has been circulating since early January 2022. Notably, viral genomes with a similar profile also have been identified in Denmark and The Netherlands. 
Additional investigation and analyses are needed to determine if these recombinants derive from a single common ancestor, or from multiple similar recombination events.

What WHO said about its severity and transmissibility?

Providing an update on the same, WHO's Maria Van Kerkhove said on Twitter, This is to be expected, especially with the intense circulation of omicron and delta. She further notified that WHO is tracking and discussing.

The WHO official, during a press conference, also asserted, currently, no changes are being observed in its severity and transmissibility, but several studies are underway on the topic. At this stage, testing remains critical.
Source : https://www.livemint.com/science/health/who-warns-of-omicron-delta-recombinant-virus-as-study-finds-1st-solid-evidence-here-s-what-it-is-11646823310138.html