Whooping cough vaccines don’t start until age two. There are CDC commercials now telling adults to get a booster to protect those who are not old enough for the vaccine. All these booster vaccines (pertusis, chicken pox, tetanus), it’s almost like they don’t do what Big Gov tells us they do!
For infants, the DTaP vaccination schedule is as follows,
2nd month - 1st dose
4th month - 2nd dose
6th month - 3rd dose
15th - 18th month - 4th dose
4-6 years - 5th dose
The vaccination for DTaP can be given after 6 weeks of age and keeping to the above schedule will be practically convenient. The 4th dose could be given as early as 12 months if 6 moths have elapsed after the 3rd dose.