Preprint data show that a three-dose combo of Soberana jabs has 92.4% efficacy in clinical trials.
When the COVID-19 pandemic began, Cuba decided not to wait on the rest of the world to develop vaccines. The United States’ 60-year-old economic embargo against the country, which prevents US-made products from being exported there, would make it difficult for Cuba to acquire vaccines and therapies, researchers and officials knew. “It was best, for protecting our population, to be independent,” says Vicente Vérez Bencomo, director-general of the Finlay Institute of Vaccines in Havana.
So the Finlay Institute and Cuba’s other state-run biotechnology centres started developing their own COVID-19 vaccines in the hope that at least one of them would be effective. Their bet seems to be paying off: in a 6 November preprint published on medRxiv, Vérez Bencomo and his colleagues report that one of the institute’s vaccines, Soberana 02, is more than 90% effective in protecting against symptomatic COVID-19 infection when used in combination with a related vaccine. Importantly, the combination seems to be effective against the highly transmissible Delta variant of the coronavirus SARS-CoV-2, which has caused surges in hospitalizations and death across the world and now accounts for nearly all COVID-19 cases in Cuba.
As of 18 November, 89% of Cuba’s population — including children as young as 2 — has received at least one dose of Soberana 02 or another Cuban vaccine called Abdala, which is produced at the Center for Genetic Engineering and Biotechnology (CIGB) in Havana. The centre reported in July that Abdala, a three-dose vaccine, was more than 92% effective in phase III trials that included more than 48,000 participants, but the full results have not yet been published.
Cuba’s regulatory agency authorized Abdala and Soberana 02 shots for use in adults in July and August respectively, and health-care workers began immunizing children with both vaccines a few months later. The country has begun exporting the two home-grown vaccines to Venezuela, Vietnam, Iran and Nicaragua. And it has asked the World Health Organization to approve its vaccines — an important step towards making them available throughout the developing world.
In developing Soberana 02, Vérez Bencomo’s group drew on its existing ‘conjugate’ vaccine technology. Finlay’s conjugate vaccines take a protein or a sugar from a bacterium or virus and chemically link it to a harmless fragment of a neurotoxin protein from the tetanus bacterium. The combination elicits a stronger immune response than either component alone. Conjugate vaccines against meningitis and typhoid are used around the world, and Cuba has been immunizing children with a vaccine of this type for years.
Vérez Bencomo’s team adapted conjugate-vaccine technology to tackle COVID-19 by linking the tetanus-toxin protein to a portion, known as the receptor binding domain (RBD), of SARS-CoV-2’s spike protein (the spike protein helps the virus to enter cells). After more than 14,000 people received two doses of the vaccine in a phase III trial, recipients’ risk of symptomatic COVID-19 was reduced by 71%, compared with that of a placebo group of the same size — an efficacy similar to jabs made by Johnson & Johnson (J&J) in New Brunswick, New Jersey, and AstraZeneca in Cambridge, UK.