Hi and Welcome to the forum.
I don’t know where you’re from but I live in the UK where bunnies need to be vaccinated.
Don’t worry, the double vaccine is totally safe and normal!
It’s actually the newer style. Having two separate vaccinations is the old way of doing it. They needed to be given at separate times and lasted different amounts of time too, so the new vaccine is much more convenient for everyone (including your bunny!)
Here is what my vet’s website says about it:
Rabbit Vaccination
There are two fatal disease of rabbits which can vaccinate against. They are spread between rabbits by biting flies, fleas and mosquitos.
Myxomatosis:
This is a disease commonly found in wild rabbit populations, it causes swelling of the face, ears and genitals. It is usually fatal. A vaccine is available for myxomatosis, the vaccines lasts 6 months.
Viral Haemorrhagic Disease:
This disease causes a very acute illness so that affected rabbits die from severe internal bleeding.
There is a new combined yearly vaccination for both of these conditions.
Hope this has put you at ease! 