Young Pfizer COVID-19 Vaccine Recipients More Likely to Get Infected After 5 Months

A health care worker fills a syringe with Pfizer's COVID-19 vaccine in a file image. Robyn Beck/AFP via Getty Images

The Pfizer COVID-19 vaccine turned negatively effective after five months, according to a new study.

Researchers with the U.S. Centers for Disease Control and Prevention (CDC) analyzed test results from sites across the United States and determined that the vaccine was 60 percent effective two to four weeks after 12- to 15-year-olds got the second of the two-dose primary regimen.