I'll talk about the advantages and disadvantages of scientific tests on animals. I think this can help to discover and cure new diseases, but always using it well.
Tests scientific can help to discover new vaccine to unfamiliar diseases. There are many laboratories are investigating animal a vaccine for cancer. These tests can certainly kill some animals, but it may save many lives.
In all laboratories when they discover a new vaccine, don´t know the effects it can have, and tested on animals, such as rats. Scientists can see the effects of the vaccine and if no bad results can be used by sick patients.
For end, my opinion is that it is okay to try the tests on animals, although some may die, but it can cure diseases, but in tests they do, they have to make them better for the least possible harm to the animals.