With a sniff or a swallow, new vaccines aim to put the brakes on Covid-19 spread

Injected vaccines against the coronavirus that causes Covid-19 have been hugely successful, saving nearly 20 million lives globally in their first year of use and slashing the pandemic's death toll by an estimated 63%, according to a recent study. Yet good as these shots are, they have not stopped the virus from spreading from person to person.   As the SARS-CoV-2 virus spreads, it changes. That has helped it get past our firewalls, the immunity created by vaccines or left behind after we recover from an infection. Which is why, well into the third year of the pandemic, we're in the midst of another wave of Covid-19 caused by the most immune-evasive variant yet, BA.5. And more variants are coming.   Even as vaccine manufacturers race to update the first-generation shots in the hopes of patching up our protection for the fall, other scientists are taking a different approach, making vaccines delivered via nasal sprays or tablets that would deploy more immune defenders to the body's front lines: the lining of the mouth, nose and throat.   "The hope is to shore up the defenses right there in the nose so that the virus can't even replicate in the nose," said Dr. Ellen Foxman, an immunobiologist at the Yale School of Medicine. "And then someone who has a really effective mucosal vaccination can't even really support viral replication or make viruses that can infect other people.   "That would be like the holy grail," Foxman said.   If it works, there's hope that mucosal immunity could slow the development of new coronavirus variants and finally bring the Covid-19 pandemic under control.   There's a long way to go before that happens, however, and many scientists say the approach needs an injection of funding to accelerate the pace of development, much in the same way the billions of dollars doled out by Operation Warp Speed delivered the first generation of Covid-19 vaccines in record time.   On Tuesday, the White House is hosting a summit to discuss the future of these types of vaccines, as well as the next generation of our current vaccines.