Transcript for Why you may need a COVID-19 vaccine booster
All right. And joining us as always, ABC chief medical correspondent Dr. Jen Ashton, so let's take a look at the latest coronavirus case numbers from Johns Hopkins university. Now more than 139.1 million cases of coronavirus confirmed around the world with more than 565,000 American lives lost. As the vaccination numbers also rise, the CDC now reporting at least 198.3 million doses administered across the country And we have been talking, Dr. Ashton, about the possibility of we might need a booster down the road. The head of pfizer now telling us we might need one in a year and the next year. This headline is getting a lost attention. Here's what you need to know. First of all, if you look at the background and the science of coronaviruses, immunity to other coronaviruses like the common cold, it doesn't last forever, so it does wane, after months or years depending on the strain. Remember, at play here, complicating this picture, new variants. Right now the vaccines are effective against them. But in the future, they may not be. It's another reason we may need boosters, so the CEO of pfizer saying, and I quote, we may need a third dose within a period of 12 months. And we've heard the chief scientific officer of the white house say, quote, expect that we may have to boost. So when people hear this headline, this should not come as a surprise. Right, not a surprise, but I think people still want to understand what is the science behind why. 100%. And that's so important. So remember, 10% to 30% of common colds worldwide are caused by the family of coronaviruses. We've all had a common cold caused by a coronavirus, and we know most people get more than one cold in their lifetime. Same principle. And also in terms of the vaccine, it's not just about antibody protection, there's also t-cells which are important, so again, that's why people in the clinical trials are being followed six months, nine months, up to two years, so that we know if at nine months, 12 months, that immunity starts to wane, that's when we'll need a booster and also a reminder why after we get vaccinated we can't just willy-nilly go back to the way things were in 2019. We still have to be cautious. All right, Dr. Jen, thank you very much.
This transcript has been automatically generated and may not be 100% accurate.