Vaccines and antitoxins, collectively known as "biologics," were made in animals, hence the possibility of contamination was large. In 1901, 13 children in St. Louis, Missouri, died from diphtheria antitoxin that had been contaminated with tetanus spores. This tragedy led Congress in 1902 to pass a Biologics Control Act that required commercial manufacturers to demonstrate the purity (and later potency) of their products. The Hygienic Laboratory was assigned regulatory responsibility. This useful activity helped to protect its more politically vulnerable research activities.