Brazil has announced that a SARS-CoV-2 vaccine developed by China's Sinovac has a lower effectiveness rate, about 50 percent, than initially thought, CNN reports.
Earlier this month, Brazil said the CoronaVac vaccine had a 78 percent effectiveness rate, but it has now revised that estimate to say the vaccine's effectiveness is 50.38 percent. According to CNBC, the 78 percent effectiveness rate was calculated among volunteers with mild to severe disease and the effectiveness rate fell when very mild cases not needing medical intervention were included in the assessment.
This, CNN notes, places the CoronaVac vaccine at the edge of what the World Health Organization has said is needed for a SARS-CoV-2 vaccine. It is also, it adds, lower than effectiveness rates reported for other vaccines. The Pfizer-BioNTech and Moderna vaccines have effectiveness rates of about 95 percent, while the vaccine from Sinopharm is 79 percent effective.
This could affect how readily the CoronaVac vaccine is adopted, according to the Council on Foreign Relations' Yanzhong Huang. "Since many countries are planning to order, or have already ordered Sinovac's vaccines, it might undermine people's willingness to take them, because people may question the usefulness of the vaccines," he tells CNN. "It could be a potential stumbling block."