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Scientists See Downsides to Top COVID-19 Vaccines from Russia, China

Reuters

   TORONTO/CHICAGO - High-profile COVID-19 vaccines developed in Russia
   and China share a potential shortcoming: They are based on a common
   cold virus that many people have been exposed to, potentially limiting
   their effectiveness, some experts say.

   CanSino Biologics' vaccine, approved for military use in China, is a
   modified form of adenovirus type 5, or Ad5. The company is in talks to
   get emergency approval in several countries before completing
   large-scale trials, the Wall Street Journal reported last week.

   A vaccine developed by Moscow's Gamaleya Institute, approved in Russia
   earlier this month despite limited testing, is based on Ad5 and a
   second less common adenovirus.

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