A health worker administers the oral polio vaccine to a young girl as other children wait for their turn at a school in Karachi, Pakistan on February 28, 2022. In response to an uptick in cases of vaccine-derived polio — a form of the disease that stems from the oral vaccine — many countries are rolling out a new oral polio vaccine. (AFP via Getty Images)
This article was originally published on April 26, 2022.
