The following are excerpts from a Medpage commentary.
Don't Jump the Gun on Boosting All Adults
For the CDC...the appearance of Omicron with its mutation profile, which includes changes that have been associated with less protection from the vaccine, was enough to universalize stronger booster recommendations for all adults. However, this action appears to be a preemptive move done without any new publicly released data to undergird it. The likely rationale behind the change may be that higher antibodies, even against an evasive variant like Omicron, may prevent infection. Though this is plausible, there isn't data yet to support this.
...for the young, healthy population, the value of boosting with the vaccine currently available to transiently prevent what would likely be non-severe illness is, to me, of marginal value. The likelihood of non-severe COVID-19 in young, healthy people is almost certain to be as true for Omicron as it has been for Delta...Amesh Adalja, MD