In 1939, Dr. Nora Wattie Principal Medical Officer (Maternity and Child Welfare) introduced immunisation clinics across Glasgow, and promoted mother and child health education, resulting in virtual eradication of the infection in the city.Widespread vaccination pushed cases in the United States down from 4.4 per 100,000 inhabitants in 1932 to 2.0 in 1937. In Nazi Germany, where authorities preferred treatment and isolation over vaccination (until about 1939–41), cases rose over the same period from 6.1 to 9.6 per 100,000 inhabitants.Between June 1942 and February 1943, 714 cases of diphtheria were recorded at Sham Shui Po Barracks resulting in 112 deaths because the Imperial Japanese Army did not release supplies of anti-diphtheria serum.In 1943, diphtheria outbreaks accompanied war and disruption in Europe. The 1 million cases in Europe resulted in 50,000 deaths.In Kyoto during 1948, 68 of 606 children died after diphtheria immunization due to improper manufacture of aluminum phosphate toxoid.In 1974, the World Health Organization included DPT vaccine in their Expanded Programme on Immunization for developing countries.In 1975, an outbreak of cutaneous diphtheria in Seattle, Washington, was reported .After the breakup of the former Soviet Union in 1991, vaccination rates in its constituent countries fell so low that an explosion of diphtheria cases occurred. In 1991, 2,000 cases of diphtheria occurred in the USSR. Between 1991 and 1998 as many as 200,000 cases in the Commonwealth of Independent States were reported, with 5,000 deaths. In 1994, the Russian Federation had 39,703 diphtheria cases.
In 1906, Clemens Pirquet and Béla Schick described serum sickness in children receiving large quantities of horse-derived antitoxin.Between 1910 and 1911, Béla Schick developed the Schick test to detect pre-existing immunity to diphtheria in an exposed person. Only those who had not been exposed to diphtheria were vaccinated. A massive, five-year campaign was coordinated by Dr. Schick. As a part of the campaign, 85 million pieces of literature were distributed by the Metropolitan Life Insurance Company with an appeal to parents to "Save your child from diphtheria." A vaccine was developed in the next decade, and deaths began declining significantly in 1924. In 1919, in Dallas, Texas, 10 children were killed and 60 others made seriously ill by toxic antitoxin which had passed the tests of the New York State Health Department. Mulford Company of Philadelphia (manufacturers) paid damages in every case.In the 1920s, each year an estimated 100,000 to 200,000 diphtheria cases and 13,000 to 15,000 deaths occurred in the United States. Children represented a large majority of these cases and fatalities. One of the most infamous outbreaks of diphtheria occurred in 1925, in Nome, Alaska; the "Great Race of Mercy" to deliver diphtheria antitoxin is now celebrated by the Iditarod Trail Sled Dog Race.In 1926, Alexander Thomas Glenny increased the effectiveness of diphtheria toxoid (a modified version of the toxin used for vaccination) by treating it with aluminum salts. Vaccination with toxoid was not widely used until the early 1930s.