Though all eyes are on omicron right now, the bulk of coronavirus cases in the United States are still from the delta variant.

But given omicrons speedy spread in South Africa, epidemiologists strongly suspect it will soon outcompete delta in many other regions across the globe. Just take a look at how rapidly omicron is ripping through the Netherlands .

While were still in the very early stages of understanding how omicron compares to delta, preliminary evidence suggests the new COVID-19 variant may be more contagious but less severe than its predecessor. But there are too many other contributing factors like how much immunity a population already has, along with seasonality and behaviors to know if that is definitively the case.

Even with all that uncertainty, epidemiologists have a few early guesses at how omicron and delta may differ. Heres what we know so far:

Omicron has more mutations than delta.

For the delta variant, the part of the spike protein that attaches to our cells is very similar to what existing coronavirus vaccines are designed to go after. But in the case of the omicron variant, the spike picked up 32 mutations that make it more difficult (though not impossible) for our immune system to recognize and prevent the virus from causing an infection.

The omicron spike is still 97% identical to the vaccine, but the changes are clustered in a way that makes it harder for the immune system to neutralize, said Benjamin Neuman , chief virologist at Texas A&M Universitys Global Health Research Complex. According to Neuman, all of the mutations in omicron have been seen before in other variants but they have never been clustered together exactly as they are in omicron.

While the vaccines may take a slight hit in efficacy, Neuman expects that antiviral drugs remdesivir, molnupiravir and Paxlovid, the coronavirus pill will remain just as effective against omicron as they were against delta and previous variants because they target parts of the virus that remain unchanged.

Though theres so much uncertainty about omicron, epidemiologists seem convinced the new variant will outcompete delta across the globe.

Omicron will displace delta as the dominant variant, just as delta replaced alpha. I think thats pretty certain, said Andrew Noymer , a University of California, Irvine epidemiologist and demographer who studies infectious diseases.