Pfizer administers its first booster shots in trial Monday

CNN– Pfizer has administered its first COVID-19 booster shots. The pharmaceutical company is studying a third dose of the vaccine and a pneumococcal vaccine candidate. The first participants received their shots Monday.

The trial is looking at safety when the vaccines are co-administered, and will follow up six months after. Pneumococcal vaccines help prevent illnesses like pneumonia. 600 adults over the age of 65 are in the trial. Some will receive both shots, and others will only receive one and a placebo.