July 20 (UPI) -- At its peak, smallpox killed nearly 30 percent of people infected by the virus. Those who survived were often crippled. But 40 years ago, after decades of vaccination efforts, the disease was eradicated.
Now, thanks to an analysis of American Civil War-era vaccination kits, scientists have traced the origins of the virus strains used during some of the earliest smallpox vaccination efforts in the United States, according to a study published Monday in the journal Genome Biology.
For the study, an international team of researchers captured viral molecules from biological material, including blisters and pus, left on blades, tin boxes and glass slides found inside the aging leather vaccination kits housed at the Mütter Museum of the College of Physicians of Philadelphia.
Analysis of the molecules revealed the genomes of virus fragments, allowing scientists to identify the strain used to vaccinate Civil War soldiers against smallpox.
In addition to highlighting the important work of vaccination, researchers suggest the study of early smallpox vaccination efforts can offer valuable lessons to scientists all over the globe, as they race to develop a vaccine against COVID-19.
"Understanding the history, the evolution and the ways in which these viruses can function as vaccines is hugely important in contemporary times," study co-author and evolutionary geneticist Hendrik Poinar said in a news release.
"This work points to the importance of looking at the diversity of these vaccine strains found out in the wild. We don't know how many could provide cross protection from a wide range of viruses, such as flus or coronaviruses," said Poinar, director of the Ancient DNA Center at McMaster University in Canada.
To vaccinate patients against smallpox, physicians used the cowpox virus, a milder relative of the smallpox virus -- a technique first developed by the English physician Edward Jenner during the late 18th century.
American Civil War soldiers enlisting in both the northern and southern armies were required to be vaccinated against smallpox.
"During the war, most of the College [of Physicians of Philadelphia] members served either in the army or as contract physicians and, as such, administered smallpox vaccination according to standard army protocol," researchers wrote in the paper.
Analysis of the viral strains recovered from the Mütter Museum artifacts showed these protocols involved the propagation of a vaccinia virus strain in human subjects. Pus or scabs from one cowpox-infected patient was collected and applied to a scratch or cut in the skin of another patient. Exposure to cowpox helped the patient develop immunity to smallpox.
Researchers involved in the development of new vaccines are constantly working to determine how close a vaccine strain must be to a target virus to produce an immune response.
The latest research showed that the vaccinia virus strain being used during and after the American Civil War was, in fact, quite distantly related to smallpox.
"Vaccination is a wonderful process with a rich medical history that we should celebrate," said lead study author Ana Duggan.
"Medical museums are incredible repositories of our past and of our collective history. The new tools we develop in this work allow us to begin to investigate how medical sources, procedures and techniques have changed through time," said Duggan, a former postdoc in the anthropology department at McMaster and now a researcher at the Public Health Agency of Canada.