What Covid vaccines will and won’t do

Vaccines are a marvel of medicine. Few medical interventions can claim to have saved as many lives. But it may surprise you to know that not all vaccines provide the same level of protection. Some vaccines stop you from getting symptomatic disease, but others stop you from getting infected too. The latter is known as “sterilizing immunity.” With sterilizing immunity, the virus can’t even gain a toehold in the body because the immune system stops the virus from entering cells and replicating. There is a subtle yet important difference between preventing disease and preventing infection. A vaccine that “just” prevents disease might not stop you from transmitting the disease to others – even if...