...

At the National Institutes for Health (NIH), Dr. Margaret Pittman developed a new assay to test the potency of pertussis vaccines in 1944, and by 1949, manufacturers were able to sell vaccine certified to be potent and sterile. She helped set the first national and international standards for the production of the vaccine. 

In 1948, pertussis became available in a combined vaccine (DTP) with diphtheria and tetanus toxoids. 

...