With a little luck and a lot of science, the world might in the not-too-distant future get vaccines against Covid-19. But those vaccines won’t necessarily prevent all or even most infections.
In the public imagination, vaccines are often seen effectively as cure-alls, like inoculations against measles.
Rather than those vaccines, however, the Covid-19 vaccines in development may be more like those that protect against influenza — reducing the risk of contracting the disease, and of experiencing severe symptoms should infection occur.
Ideally, vaccines would prevent infection entirely, inducing what’s known as “sterilizing immunity.” But early work on some of the vaccine candidates suggests they may not stop infection in the upper respiratory tract — and they may not stop an infected person from spreading virus by coughing or speaking.
[Epidemiologist Michael] Mina sees a potential upside to Covid-19 vaccines that don’t stop infection and transmission, saying low-level circulation of the virus could act as a natural “booster” to keep people’s immunity levels high.
“Then you don’t necessarily have to keep going and getting a vaccine every year, for example. You could rely on some level of natural exposure as long as all the people who are at particular risk have been given the opportunity to be vaccinated as well,” he said.