Scientists see downsides to top Covid-19 vaccines from Russia, China

FILE PHOTO: A scientist works inside a laboratory of the Gamaleya Research Institute of Epidemiology and Microbiology during the production and laboratory testing of a vaccine against the coronavirus disease (COVID-19), in Moscow, Russia August 6, 2020. The Russian Direct Investment Fund (RDIF)/Handout via REUTERS

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.