World’s First Conjugate Vaccine for COVID-19

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    Recently, Cuba has developed the world’s first conjugate vaccine for COVID-19.

    About

    • Cuba’s State­run corporation, BioFarma, mentioned that its indigenously produced Soberana 2 vaccine, when delivered with a booster shot of Soberana Plus, was 91.2% efficacious in phase­3 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.

    (Image Courtesy: TH )

    About Conjugate Vaccine 

    • Definition: A conjugate vaccine is a type of vaccine which combines a weak antigen with a strong antigen as a carrier so that the immune system has a stronger response to the weak antigen.
    • Economical approaches used: Developed by most economical approaches. And Cuba has great knowhow about the technology for the vaccine’s development.
    • Procedure and Working: From protein S ­ the antigen or part of the SARSCoV2 virus that all COVID vaccines target because it induces the strongest immune response in humans ­ 
      • Cuban vaccine candidates are based only on the part that is involved in contact with the cell’s receptor: the RBD (receptor binding domain) which is also the one that induces the greatest number of neutralising antibodies­ 
    • Common example of its use: The most common conjugate vaccines are those used for Haemophilus influenzae type b and the pneumococcal bacteria.
      • Cuba had already developed another vaccine with this principle. It is CheimiHib, ‘the first of its kind to be approved in Latin America and the second in the world’, against haemophilus influenzae type b, coccobacilli responsible for diseases such as meningitis, pneumonia and epiglottitis
    • Unique fact of Soberana: 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
    • Subunit vaccine: Both, Abdala and Soberana, 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, 
      • 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. 
    • Generally used against Bacteria: While there are no inherent disadvantages to taking a conjugate vaccine approach for coronavirus vaccines, they have generally been used against bacteria and not viruses. 
    • For effective response: 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. 
    • Could prove to be most effective: In a protein sub­unit 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 T­cell response could also be generated and conferring more effective protection

    Conclusion

    • The conjugate vaccines have several advantages and their use could be promoted as they result into:
      • Improved immune and memory response,
      • Longer lasting protection,
      • The protection of infants and toddlers,
      • Their effect on bacterial carriage,
      • The creation of herd immunity.
    • The conjugate vaccines have a superb safety record and have been associated with very few, serious adverse events following immunization (AEFIs) after more than 20 years of use. 
    • India should also show adequate interest in Cuban Vaccines to strengthen its vaccination drive. 

    Sources: TH