Question: Can you catch coronavirus more than once or are you permanently immune like after measles or something?

Answer: Short answer: We aren’t sure. Longer answer: We currently know that COVID-19 can stay circulating in a person for several weeks after recovery (see Q&A from 3/9). Good news: Some epidemiologists think this may be beneficial for longer-term protection since it gives your body’s immune system a longer time to build effective antibodies; There was a really small study of Macaques and reinfection released on March 14 that has not yet been peer reviewed and is not necessarily applicable to humans, which shows that over a short time, Macaques were not able to be reinfected with COVID-19. Bad news: We also know that viruses mutate (see Q&A from 3/11), which may create a different strain that a body’s immune system will have to mount a new response to. And we know that a person stays immune to another type of coronavirus — the common cold — for only 1–2 years after getting it. Finally, scientists are also hypothesizing that there is a dose-response relationship with COVID-19 — the more a person is exposed, the more severe the disease — scientists observed this phenomena with SARS. In summation: It seems there may be degrees of “catching COVID-19” (bad news especially for health care workers), that once you catch it, the virus may not be fully gone even when you are recovered, and our longer-term immune response is still unknown.

Question: Would you explain the threat that covid-19 poses to immunodeficient communities? And how that can impact our society as whole as well? Personally, I have a lot of loved ones with other health conditions, everything from asthma, to Crohn’s disease to transplant recipients on immunosuppressants. A lot of them are “young” and otherwise “healthy” people, but it is still scary to think about what would happen if one of them became ill with covid-19. And from my understanding, people with other health conditions are no small percentage of our population.

Answer: Per most of my answers, we have limited data about COVID-19 since it’s new and our knowledge is still growing. But, we can explore this good question with existing information. First, let’s look at the proportion of adults who are immunocompromised in the United States. I’ve copied herein a table from a 2016 research letter in JAMA that explores prevalence of immunosuppression among US adults. What we see is that among those 18–39, the prevalence is 1.6%, which is the equivalent of about 1.5 million Americans ages 18–39. Based on existing knowledge, we would expect an immunocompromised person to have more serious complications of a respiratory disease like COVID-19 as they have a weakened immune system that just isn’t as well equipped to fight against the “intruder”. Research on other types of respiratory infections — here, influenza — shows that “Immunocompromised patients with influenza had more severe disease/complications, longer viral shedding, and more antiviral resistance while demonstrating less clinical symptoms and signs on clinical assessment.” So, not only would we hypothesize that immonocompromised individuals would have more serious complications of COVID-19, we might also hypothesize that they are at increased risk of transmitting COVID-19 to others. For more on how the immune system works, check out this good article from Bulletin of the Atomic Scientists. CDC has also recently issued COVID-19 guidelines for people living with Asthma and people living with HIV, and has offered guidance to healthcare providers on how to handle immunocompromised patients. In short, even if you are young, if you are immunocompromised, please take additional precaution to protect yourself from COVID-19.