The primary goal of a COVID-19 vaccine is to keep people from getting very sick and dying. But there’s another goal — to prevent the spread of the disease — and it’s not clear most vaccine candidates currently under development can do that.
Some scientists think they can solve that problem by delivering a vaccine as a nasal spray.
“The majority of vaccines — in fact all of the ones that are currently in clinical trials — are delivered via the muscle,” says Frances Lund, an immunologist and vaccine developer at the University of Alabama, Birmingham. That muscle is typically the deltoid in the upper arm. An injection into muscle tends to give the strongest immune response. That’s why most vaccine developers start there.
“You will get a systemic response, but you will not get a local response with that,” she says. By systemic response, Lund is talking about generating