When will centre start administering precautionary dose for health workers and senior citizens with co-morbidities?

PM Narendra Modi announced on December 25, 2021 that the government has decided to start a precautionary dose of COVID vaccine for Healthcare and Frontline Workers and citizens above 60 years of age with co-morbidities from January 10, 2022. The senior citizens will need a comorbidities certificate to take the dose.