The results of the phase three ENSEMBLE clinical trial have shown that Johnson & Johnson’s single-shot Janssen COVID-19 vaccine candidate is 66 percent effective overall at preventing moderate to severe COVID-19 cases 28 days after vaccination.
The study also showed that the vaccine provided 85 percent effectiveness overall in preventing severe cases and complete protection against hospitalization and death as of day 28.
However, its efficacy against moderate and severe disease notably varied from one country to the next: 72 percent in the United States, 66 percent in Latin America, and 57 percent in South Africa, where a more contagious and antibody-resistant strain of COVID-19 has taken root. In all, 43,783 patients participated, and 468 symptomatic cases of COVID-19 resulted.
“Our goal all along has been to create a simple, effective solution for the largest number of people possible, and to have maximum impact to help end the pandemic,” Alex Gorsky, chairman of the Board of Directors and CEO of Johnson & Johnson, said. “We’re proud to have reached this critical milestone, and our commitment to address this global health crisis continues with urgency for everyone, everywhere.”
According to U.S. Food and Drug Administration (FDA) standards, a vaccine is considered effective once it reaches 50 percent efficacy or higher. Former FDA Commissioner Scott Gottlieb applauded Johnson & Johnson’s “fantastic result” on Twitter, stating that “The milieu of disease now is more complex; even in U.S. – trials done today are running into more mutated cases. Make no mistake: this is an important and wonderful development.”
Notably, the drug’s efficacy against severe disease increased over time, with no cases in vaccinated participants reported after 49 days. The onset of protection was observed as early as day 14, and protection to severe cases was generally consistent across race, age groups, and all variants and regions studied.
“These topline results with a single-shot COVID-19 vaccine candidate represent a promising moment,” said Dr. Paul Stoffels, vice chairman of the Executive Committee and Chief Scientific Officer at Johnson & Johnson. “The potential to significantly reduce the burden of severe disease, by providing an effective and well-tolerated vaccine with just one immunization, is a critical component of the global public health response. A one-shot vaccine is considered by the World Health Organization to be the best option in pandemic settings, enhancing access, distribution, and compliance.”
Participants in ENSEMBLE will continue to be studied for up to two years to fully determine safety and efficacy.