February 28, 2022 8:01 PM ET VANESSA ROMO ROB STEIN A medical staff member prepares a Pfizer-BioNTech COVID-19 vaccine at a pop-up site in New York City last October. Michael M. Santiago/Getty Images The low-dose version of the Pfizer-BioNTech COVID-19 vaccine appears to be much less effective at protecting young children against infection than the...
