Andrew Sherman, a Covid-19 survivor, is finally starting to feel better. One of the first things he did during his recovery: volunteer to donate blood plasma to help seriously ill patients fight the disease.

Mr. Sherman, age 52, spent three days on oxygen in a New York City hospital in mid-March before being released to complete his recovery at home in the Williamsburg section of Brooklyn, where he lives with his wife, Jodi Sheeler, and their two children: Maisy, 8, and Milo, 11.

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