The highly contagious delta variant makes up about 83% of current COVID-19 cases in the U.S.

Now there is a race to get more Americans vaccinated. BioNTech and Pfizer just announced the U.S. government has purchased an additional 200 million doses of their COVID-19 vaccine for continued supply.

That brings the total number of Pfizer vaccines supplied to the U.S. to 500 million.

This comes as a new study from the New England Journal of Medicine shows two doses of the Pfizer shot was 88% effective at preventing symptomatic disease from the delta variant.

Dr. David Hirschwerk, an infectious disease specialist at Northwell Health, answers your questions.

Is there any information about the Moderna vaccine and protection against the delta variant?

Many college kids had COVID-19 and fully recovered. Do they have antibodies at a higher level than vaccinated people? Why should they get vaccinated?

Should those who are immunocompromised and received the Johnson & Johnson vaccine consider getting a different one?