A young doctor tries an untested vaccine to save her brother’s life which results in a virus that destroys the world as we know it. She now has to lead a group of young survivors to safety. Trying to avoid a world of infected people and scavengers, while being hunted by something they’ve never seen before.

Or you could focus on the emotional level.

After causing an world ending pandemic a doctor seeks redemption by trying to lead survivors to safety.

The inciting incident feels wrong on account of her creating the problem in the first place. If it were the case that the problem was created by someone else and she had to fix it, then she would come across as a hero, not someone trying to fix her own 'F' up. Even if it only seemed that way in the logline and for most of the story it would work. Why not simply cut the first sentence? Then you can start the logline with 'After a pandemic wipes out most of life on Earth...' - that's a big deal and a significant inciting incident.

The twist is that she was the cause for it can come in later, but mentioning it in the logline dilutes the impact of the premise - you'de be better off hiding the twist and not revealing it until act three.

"...Trying to avoid a world of infected people and scavengers..." - this is stock standard post-apocalypse fare. Is there anything unique about the specific dangers that this group of unwitting survivors must face?