1.
A large number of people have been vaccinated against the H1N1 flu, in fact, eighty million!
2.
A large number of people have been vaccinated against the H1N1 flu. in fact, eighty million people have!
3.
A large number of people have been vaccinated against the H1N1 flu; in fact, eighty million people have!
vaccinate – to protect a person or animal from a disease by giving them a vaccine, injection
Note that written and spoken English differ in regards to a sentence. While a spoken sentence needs only a complete thought and can rely more heavily on contextual information, a written sentence needs a clear subject and a verb to be grammatical.
