Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Name the least interval between doses for minimum age being 1st dose at 6 weeks old for the diphtheria-pertussis-tetanus vaccine?

### Inputs:
table_name: table, columns: ['Vaccine', 'Minimum Age at 1st Dose', 'Number of Doses', 'Dose', 'Minimum Interval Between Doses', 'Route']

### Response:
SELECT Minimum Interval Between Doses FROM table WHERE Minimum Age at 1st Dose = 6 weeks old AND Vaccine = diphtheria-pertussis-tetanus vaccine