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Smallpox in Philadelphia, 1925


Carly Roche

September 27, 2016


Carley Roche, an intern here at The College of Physicians of Philadelphia, wrote today's blog post.


In December 1924 the city of Philadelphia experienced an uptick in the incidence of smallpox with 9 new cases of the disease. While there had been a few reported cases earlier in the year, it soon became apparent in early January 1925 that the December outbreak might be more severe than the others, as the first smallpox death occurred in Philadelphia in more than 12 years. The Department of Public Health would spend the next 6 months quarantining and vaccinating citizens of the city in order to prevent a massive outbreak of smallpox beyond the city limits.

From January 1, 1925, to June 30, 1925, 183 cases of smallpox were reported in Philadelphia, resulting in 23 deaths. Due to the sudden rise in cases the Department of Public Health established police-enforced quarantines throughout the city. If a person was found to be infected, the police would ensure that the patient, and anyone who came into direct contact with her/him, would be kept from the public for 18 days. And, as the number of cases grew with each passing week, so did the number of people getting smallpox vaccine, though some refused the immunization. Resistors, however, were subject to police-enforced quarantine for a maximum of 18 days.

The chief medical inspector at the time, Dr. A.A. Cairns, took vaccination within the city very seriously. In 1904 Dr. Cairns took over as chief medical inspector of Philadelphia and had a history of vaccinating people in order to prevent outbreaks. In 1910 he and a team of physicians personally vaccinated 700 people on a ship before they were allowed into Philadelphia due to a smallpox outbreak on the vessel. Again in 1923 Dr. Cairns showed his enthusiasm for vaccination when he learned that a smallpox patient had attended a local church. He went to the church with a police force and demanded that the congregation be vaccinated. In all, 3,500 residents of northeast Philadelphia received the smallpox vaccine during the 1923 outbreak.

When the smallpox outbreak hit Philadelphia in 1925, it is no surprise then that Dr. Cairns jumped into action to prevent the spread of infection. Having set up a system of quarantine and vaccination, Dr. Cairns still felt more could be done. In April 1925 he met with Mayor W. Freeland Kendrick and the president of the City Council to request more funding and staffing in the fight against smallpox. With immediate and unanimous support for his wishes, Dr. Cairns left the meeting with a plan to divide the city into three sections. Each section was then placed under the charge of an assistant diagnostician. Dr. Cairns and his team worked tirelessly to contain the smallpox outbreak. About 200,000 people were vaccinated by the Department of Public Health while another 300,000 were vaccinated by hospitals, institutions, industrial plants, or their own physicians.

The last reported case occurred of the 1925 outbreak occurred on June 11, 1925. Only 11 of the city’s 66 wards had been untouched by the disease. The fact that smallpox did not escape past Philadelphia’s city limits in 1925 is a testament to the widespread vaccination and quarantining of sick individuals. Once the epidemic ceased it was widely believed had Dr. Cairns and his team not implemented these tools the city would have faced a more severe epidemic that could have lasted for nearly 20 years.

It was noted during the epidemic that more cases were reported during colder months. The Bureau of Health warned in their monthly bulletin after the outbreak, “…without fear of exaggeration, that there are still about one million people in this city who should be vaccinated or revaccinated before the onset of colder weather if we are to feel adequately protected against the advent of a smallpox epidemic within the next year or so.” Smallpox was believed to thrive in cold weather, and medical workers in Philadelphia pleaded for all to be vaccinated even in the summer so that cases wouldn’t surge in the coming winter.

Today smallpox has been eradicated. The last reported case in the United States occurred in 1949, and the last wild case of smallpox occurred in 1977 in Somalia. In the years since smallpox was eradicated, only people who work closely with the disease in a laboratory setting or who would be first responders in the event of a bioterror attack receive the vaccine. Even so, from our post-eradication standpoint, it is still important to remember Dr. Cairns, his team, and their effort during the first half of 1925 to contain smallpox from becoming a wider epidemic. Dr. Cairns himself had an idea that smallpox could eventually be defeated. He wrote, “If every infant were vaccinated before the first six months of life, and again at the age of puberty smallpox would be an unknown disease.” Dr. Cairn’s prediction that smallpox would one day be defeated turned out to be true, and his legacy continues in the work of healthcare workers who remain devoted to eliminating vaccine-preventable diseases.  



  • Cairns, A.A, M.D. Features of the Smallpox Situation in Philadelphia in 1925. In: . Philadelphia, PA: Dornan; 1925: 255-260.
  • Centers for Disease Control. Center for Disease Control and Preparedness.
  • Department of Public Health of the City of Philadelphia. Report of the Smallpox Outbreak in Philadelphia 1925: With a Review of Smallpox and Vaccination. Monthly Bulletin of the Department of Public Health of the City of Philadelphia. June and July, 1925: Vol. 10 No. 6 and 7.
  • . Journal of the American Medical Association. May 24, 1913: Vol. 60 Part 2
  • Reyburn, John E. Annual Report of …mayor of Philadelphia. Philadelphia: Dunlap Printing Co.; 1910.


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