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People who have recovered from COVID-19 may worry about lingering health effects, but some may also focus on what they see as the good news: Now they are immune. Or are they?

It's true that the number of reinfections has been small—about two dozen reported from more than 41 million cases globally. While scientists are learning more about how the immune system responds to the novel coronavirus, SARS-CoV-2, that causes COVID-19, many questions remain.

Getting more specific answers about how the immune system responds to the virus, including whether recovery is likely permanent, is crucial not only to those who have recovered. These answers can help inform vaccine makers to make the most effective vaccines as well.

To get the answers, scientists are studying immune responses of infected people. They are also looking back at other serious viral diseases, such as Ebola, to see if they can apply the knowledge about immunity from those conditions to COVID.

Go to WebMD to learn more about COVID-19 immunity.