How Effective Is the First Shot of the Pfizer or Moderna Vaccine?

March 19, 2021

(The Conversation) – As the COVID-19 vaccines reach more people across the country, some people have asked: Could we delay the second dose of the Pfizer and Moderna vaccines to allow more people to be vaccinated more quickly? And, how safe am I after my first dose?  As an immunologist, I hear this question frequently. The answer is that a single dose is very effective – but I would add that you should still get both doses. The issue is important, however, not only for your personal health but also for the country’s health as leaders figure out how to ensure there’s enough vaccine for everyone who wants one.