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Friday, February 5, 2021

Safety and efficacy of an rAd26 and rAd5 vector-based heterologous prime-boost COVID-19 vaccine: an interim analysis of a randomised controlled phase 3 trial in Russia

Sputnik V Covid Vaccine As published in The Lancet, the interim analysis of the phase 3 trial of Gam-COVID-Vac showed 91·6% efficacy against COVID-19. The scientists used adenovirus vectors, rAd 26 and rAd5, to deliver a Covid viral antigen to the immune system for recognition and immune response. Adenoviruses are among the common cold virus. So, in essence, they used a common cold virus to deliver a payload to our bodies. It's a clever approach because adenoviruses are well adapted to infecting the respiratory tract. Using one virus as a vector to deliver a payload is a known technique. For example, using the poliovirus as a vector to deliver anti-cancer treatment for recurrent glioblastoma (a type of brain tumor). It will be curious to see how well the immune response holds up for different age and health risk demographics over time. The human immune system is quite familiar with many strains of adenoviruses so we may have circulating antibodies against the adenovirus vectors which may make the immunogenic response variable in some hosts and variable over time. The same holds true for all of the authorized Covid vaccines. It will be interesting to see how the immunity holds up over time.
from Rajesh Harrykissoon, MD

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