By Jill Pease
A decade ago, Ira Longini, Ph.D., and colleagues published groundbreaking study results in the journal Lancet demonstrating that a new vaccine tested during an Ebola outbreak in Guinea was highly effective at preventing Ebola disease.
Now in a pair of new studies, Longini, a professor in the Department of Biostatistics at the University of Florida College of Public Health and Health Professions, and fellow scientists report continued success in containing or controlling Ebola outbreaks, which continue to pop up regularly in sub-Saharan Africa.
The approaches described in the papers could be used effectively during outbreaks of filoviruses, including Marburg and Sudan viruses, Mpox and a host of other infectious diseases, Longini said.
“Using rapid targeted methods for infectious disease control with effective vaccines or therapeutics is by far the best strategy for containing spread and protecting us, whether that’s against a new threat, or an old one, such as measles,” said Longini, a member of UF’s Emerging Pathogens Institute.
During the Ebola outbreak that began in Guinea in 2013 and claimed more than 11,000 lives, Longini and his colleagues at the World Health Organization designed a clinical trial to test a new vaccine that is now licensed and known as Ervebo. The team decided to use a ring vaccination design, which targets people in contact with those who have contracted the virus, including family members, neighbors and co-workers. It was also used in the eradication of smallpox.
“We showed with ring vaccination that it was possible to both evaluate a new experimental vaccine in the field during an outbreak and partially control the outbreak at the same time,” Longini said.
In a recent paper published in the New England Journal of Medicine, Longini and co-authors describe the use of a ring vaccination strategy during a later Ebola outbreak that originated in the eastern Democratic Republic of Congo. In this 2018-2020 outbreak, health care workers vaccinated contacts and contacts-of-contacts of people infected with the virus, for a total of more than 265,000 people vaccinated. Of those, the researchers followed more than 100,000 vaccinated contacts. They found that the sooner control measures, including vaccination, were implemented, the sooner Ebola rates fell among the contacts, particularly around day 10 after vaccination. The findings reinforce evidence from the Guinea trial that the Ebola vaccine is highly effective 10 or more days after vaccination.
A study published this month in the International Journal of Infectious Diseases describes the development of a model by Longini and colleagues used to estimate the impact of ring vaccination during the Democratic Republic of Congo Ebola outbreak. Compared to a hypothetical scenario of no vaccination, the ring vaccination method is estimated to have prevented 54% of potential cases in the city of Beni, and nearly 63% of potential cases in the cities of Butembo and Katwa.
Studies like these, including the publication by the team of a World Health Organization core protocol for implementing all three phases of vaccine trials to prevent filovirus infections, help to move public health policy toward systematic global control of infectious disease threats, Longini said. While Ebola may not currently pose much of a threat to the U.S., it is critical that control strategies be swiftly implemented to save lives and prevent the virus from evolving rapidly into a strain that is more transmissible and spreads easily to other continents.
“Before 2020 we used to say that the virus that causes severe acute respiratory syndrome, or SARS, only caused small outbreaks,” Longini said. “Then, suddenly we had SARS-CoV-2, a coronavirus that had evolved to the point where it was highly transmissible and caused a global pandemic.”
Support for the work was provided by the National Institutes of Health, the World Health Organization and multiple funding agencies.