I have had a bit of experience with removing smells from cars, tend to do an interior detail once a week at least.
To get the best result what I would do is remove all seats and carpet as it may be under the carpet and the only way to be sure is to take it all out.
Then properly shampoo the carpet and seats, Godfreys has an awesome little machine that pays for itself, the Bissel little green machine, a few hundred but money well spent. One word of warning it is small so will take a long time, but it works.
Also before this get some commercial grade carpet shampoo from the same shop, and they also sell a little bottle of awesomeness called sensation that neutralises smells, and other stuff, use it as a pre soak.
Keep shampooing it until its fully clean, then let it dry in the sun, and make sure its fully dry before you put it back in.
Then you have the door trims, maybe headlining, plastics, etc, it could have gotten everywhere. Use the same products on soft furnishings, and on any hard plastics (including under the carpet) steam cleaning is the best, the cheap ALDI ones aren't too bad but it will take a while again.
This will work to properly remove and clean the smell out of your car, it will take a lot longer then commercial grade equipment but it works.
I haven't cleaned vomit before, but I have cleaned bad milk stains out of hot cars which is similar, that smell is horrendous. I used these products and shampooed the carpet, seats, etc without taking the carpet out as that would have cost the customer heaps more, but it turned out pretty good, high 90% removal but if I could have removed the carpet I probably would have got rid of it 100%
Just some tips that you might find useful.
And one last thing, if you do have access to a steam cleaner, then try to clean out the air vents with it, just spray that steam all the way around in there.
The vents will accumulate tons of smells especially if you were using the air con on recirc and steaming them kills most of that smell.
Also replace your air con filter.
If none of this works find someone who has an ozone generator and knows how to use it (some detailers have them) and get them to remove all remaining smells that way.