Name the least age for the 1st dose for 3 doses of 2-3 drops
CREATE TABLE "routine_immunization_schedule_for_infant" (
  "vaccine" text,
  "minimum_age_at_1st_dose" text,
  "number_of_doses" text,
  "dose" text,
  "minimum_interval_between_doses" text,
  "route" text
);
SELECT "minimum_age_at_1st_dose" FROM "routine_immunization_schedule_for_infant" WHERE "number_of_doses"='3 doses' AND "dose"='2-3 drops';