I cannot fathom why were is used in the below highlighted sentence. Why can it be used in this way? I have got suggestions that this sentence is typical of the subjunctive mood to hypothetically discuss what has not existed yet, roughly meaning that if a vaccine for Covid-19 were available now, it would protect those vaccinated from the disease. But is it?
Looking forward to your insights. The following text is an excerpt from the Briefting section of the lastest the Economist issue, just to give you enough context of the sentence in question.
For a vaccine to get from phase I to phase III trials in just ten months, as rvsv-zebov did, was unheard of at the time—a startling example of what urgency and organisation can do. Now a repeat performance, ideally taken at an even faster tempo, is the sum of the world’s desire. In the middle of April more people are dying of covid-19 every three days than died of Ebola in west Africa over three years. A vaccine would not just save lives; it would change the course of the pandemic in two separate, if related, ways. It would protect those who were vaccinated from getting sick; and by reducing the number of susceptible people it would prevent the virus from spreading, thus also protecting the unvaccinated.