Pfizer begins testing COVID-19 booster shot with pneumococcal vaccine

Pfizer began administering its first COVID-19 booster shots Monday.

The pharmaceutical company is studying a third dose of the vaccine and a pneumococcal vaccine candidate.

The trial is looking at safety when the vaccines are co-administered, and will follow up six months later.

Pneumococcal vaccines help prevent illnesses like pneumonia.

Six hundred adults over the age of 65 are in the trial.

Some will receive both shots, others just one shot and a placebo.