The workers at the lab "were tested and there was no evidence found of Covid antibodies."
https://www.cnn.com/2021/05/23/politics/us-intelligence-repo...
So theoretically it's possible that three workers at the lab were sick -- and hospitalized -- but with, say the seasonal flu. The original reports from the State Department about this even specified that the workers had been sick with symptoms "consistent with both COVID-19 and common seasonal illness."
https://www.marketwatch.com/story/new-report-of-illnesses-at...