Your questions, answered "Vaccinated people are getting breakthrough coronavirus cases. Is it likely to get a second breakthrough case, or only if it's a different variant? How close are we to this being like colds where we can keep catching it again and again? I'm wondering about school exposures." — Michelle in Maryland Some fully vaccinated individuals have indeed contracted covid-19, the illness caused by the coronavirus. But these breakthrough infections are not common. And although it's not unheard of, health experts say it would be far less likely to have it happen twice. Although scientists do not have concrete data on the number of breakthrough cases — because many are asymptomatic or mild and not reported — the rate is thought to be low. Emerging research shows people who are vaccinated are eight times less likely to get covid-19 and 25 times less likely to have a case resulting in hospitalization or death, according to the Centers for Disease Control and Prevention. Out of more than 181 million people in the United States who had been fully vaccinated by Sept. 20, only 14,643 (or about .008 percent) were reported to be hospitalized with a nonfatal breakthrough infection, and 4,493 others died, according to data from the CDC. "It's unusual to get a breakthrough case at all, but even more unusual to get a second breakthrough case," said Roy Gulick, chief of the Division of Infectious Diseases at Weill Cornell Medicine in New York City. Gulick said there are a couple of reasons why someone might have a breakthrough case. First, not everyone mounts a robust immune response from the coronavirus vaccine. Immunocompromised individuals — including those who have certain cancers, those who have had organ transplants, those with advanced or untreated HIV, or those who are on immunosuppressive medications for autoimmune or chronic inflammatory conditions such as lupus, multiple sclerosis and rheumatoid arthritis — may not respond well, or at all, to the vaccine. Second, even healthy people's immune responses can wane over time. That why the Food and Drug Administration and the CDC have authorized an extra dose for some people with compromised immune systems or others who are at high risk. But no, breakthrough infections are not likely to become a regular occurrence, certainly not like the common cold. Colds are actually caused by many different viruses — most commonly rhinoviruses, but also adenoviruses and even some of the older coronaviruses, Gulick said. He said SARS-CoV-2, the virus that causes covid-19, is one virus that has mutated into a number of different variants, such as the highly contagious delta variant. "And the good news is that the vaccines seem to provoke an immune response that's active against all the current variants," he said. However, he added that there seems to be a "modest" decrease in vaccine effectiveness with the delta variant. If you have had a breakthrough case, the good news is you will mount a new immune response to that virus on top of the response from the vaccine, further strengthening your immune system to fight future infections. "That's why a second — or third — breakthrough infection is very unlikely," Gulick said. | 
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