I disagree tx, of the 5 whom have withdrawn only Jessie Royer is from out of Alaska and would encounter the travel issues you describe.
Not saying that vax is the issue either tho. There are also several Alaskan and Canadian teams making the travel and signed up for the Beargrease.
Regarding Jessie, she is signed up for the Idaho Sled Dog Challenge -
https://idahosleddogchallenge.com.
That race, along with the Eagle Cap Extreme and Race to the Sky, is a part of the Rocky Mountain Triple Crown series. She doesn't show entered for the Eagle Cap and the Race to the Sky site, as usual, has very little info.