More Than 80% Of Teachers, Staff Have Received 1 Dose

As of the end of March, CDC data shows that approximately 8 million teachers, staff, and childcare workers have received at least one COVID-19 vaccination. Teachers unions have advocated for educators to be vaccinated before returning to in-person learning.

What was the context in which the CDC data was mentioned?

What was the concern related to in-person learning mentioned in the text?