With so many people vaccinated against Covid, why do surges keep happening? Elizabeth Tracey reports


When enough people in certain geographic areas choose not to be vaccinated against viral diseases, outbreaks happen. We’ve been seeing this nationally with measles for years, and Covid-19 is no exception. Anna Durbin, an infectious disease expert at Johns Hopkins, explains.

Durbin: It’s all about who’s susceptible to infection. You can have in your state for instance 70% of adults vaccinated but you could have 90% of those adults in one place. When it burns through, when it gets transmitted through and it now longer has susceptible people to infect we see reduction in infections. Unfortunately then, delta came in which was more highly transmissible, so it was able to infect when alpha wasn’t. It was able to infect more people at a time than alpha.  :31

Durbin notes that because it isn’t possible to determine who’s vaccinated and who’s not, remaining vigilant is your best strategy. At Johns Hopkins, I’m Elizabeth Tracey.