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Prior to the 20th century drugs were generally produced by small scale manufacturers with little regulatory control over manufacturing or claims of safety and efficacy. To the extent that such laws did exist, enforcement was lax. In the United States, increased regulation of vaccines and other biological drugs was spurred by tetanus outbreaks and deaths caused by the distribution of contaminated smallpox vaccine and diphtheria antitoxin. The Biologics Control Act of 1902 required that federal government grant premarket approval for every biological drug and for the process and facility producing such drugs. This was followed in 1906 by the Pure Food and Drugs Act, which forbade the interstate distribution of adulterated or misbranded foods and drugs. A drug was considered misbranded if it contained alcohol, morphine, opium, cocaine, or any of several other potentially dangerous or addictive drugs, and if its label failed to indicate the quantity or proportion of such drugs. The government's attempts to use the law to prosecute manufacturers for making unsupported claims of efficacy were undercut by a Supreme Court ruling restricting the federal government's enforcement powers to cases of incorrect specification of the drug's ingredients.

What caused a law outbreak?
unanswerable