See the links & dates for each, below:

Pfizer-BioNTech COVID-19 Vaccine Clinical Trials

Actual Study Start Date : May 15, 2021
Estimated Primary Completion Date : April 1, 2022
Estimated Study Completion Date : July 30, 2023

[link to clinicaltrials.gov (secure)]

Moderna COVID-19 Vaccine Clinical Trials

Actual Study Start Date : July 27, 2020
Estimated Primary Completion Date : October 27, 2022
Estimated Study Completion Date : October 27, 2022

[link to clinicaltrials.gov (secure)]

Johnson & Johnson COVID-19 Vaccine Clinical Trials

Actual Study Start Date : September 7, 2020
Actual Primary Completion Date : January 22, 2021
Estimated Study Completion Date : January 2, 2023

[link to clinicaltrials.gov (secure)]