Cuba’s State-run corporation, BioFarma, said that its indigenously produced Soberana 2 vaccine was 91.2% efficacious in phase-3 trials. This follows closely on an announcement that another of its vaccines, Abdala, had reported an efficacy of 92.8% in late stage trials.
The greater-than-90% efficacy puts them in a select league; however, unlike the Pfizer-BioNTech and Moderna vaccines that had reported an efficacy of over 90%, both the Soberana and Abdala are three-shot vaccines.
Both are subunit vaccines, meaning that a part of the virus forms the antigen and is hitched on to another construct. In Abdala the spike protein of the coronavirus is combined with a chemically manufactured adjuvant, whereas in Soberana 2, the spike protein is chemically linked to the tetanus toxoid, making it a conjugate vaccine. The design and manufacturing allows the vaccine to be stored in regular refrigeration settings of 2–8 degree Celsius.
Conjugate vaccines: The most common conjugate vaccines are those used for Haemophilus influenza type b and the pneumococcal bacteria. However, a unique aspect of the Soberana vaccine is that it is by far the only one among coronavirus vaccine candidates that relies on the conjugate vaccine technology.
For an effective vaccine response, not only antibodies but even killer T-cells, or those produced by the immune system and capable of destroying infected cells, must be produced. In a protein sub-unit vaccine, the spike protein may be able to elicit a strong antibody response but when combined with the tetanus toxoid, a very widely used childhood vaccine and therefore one which the immune system recognises, such a T-cell response could also be generated and conferring more effective protection.
In total, the Soberana 2 is delivered through a three dose regimen. Two shots of Soberana 2 and one of Soberana Plus, when taken in a 0-28-56 day regimen, have an efficacy of 91.2 percent, the Cuban government’s Covid-19 task force announced.
