Pronoun reference

[contact.sumeshn]

I often get confused with the following type of questions:

Even today, a century after Pasteur developed the first vaccine, rabies almost always kills its victims unless they are inoculated in the earliest stages of the disease.

I am of the opinion that "its" in the above sentence is ambiguous as it can refer to both "rabies" and "first vaccine". Please let me know if i am missing something here.

Thanks!