Are abstract submissions enough to put in an update letter?

I want to submit an update letter to schools I have sent a secondary with no interview invite, but have been seeing conflicting information about whether abstracts are "enough" to include in a letter.

I have one abstract that was accepted to an international conference but I did not attend to present/poster. And we are about to submit like 5-6 abstracts where I will be included as an author (1 first, a couple 2nd/3rd, and some just in a bigger list) but the conference doesn't send out abstract acceptances until April. I don't think our lab has ever really had abstracts rejected so I'm not really worried about that-- but I've been reading that some people don't think it's worth it to include abstracts that are not yet accepted? Some said even accepted abstracts don't mean anything, only accepted papers?

I don't want to wait until April (when the abstracts will be accepted) to send an update letter, that feels way way to late.

I currently have a full-time job as a clinical researcher so that's the only thing I have really done since submitting app. I honestly have nothing else to update as my volunteer hours are pretty regular and I have not started any other activities since the initial app submission.