There will be no mix-and-match of vaccines for the crucial third dose to be given in view of the Omicron variant that is rapidly spreading in the country, senior health ministry sources told NDTV today. Precaution doses will be a third dose of the same vaccine a person has taken -- be it Covishield or Covaxin. The key aspect will be gap -- the third dose will be administered 9-12 months after the second dose to health and frontline workers and senior citizens with co-morbidities, sources said.