Vaccine also prevented 85 percent of severe Covid-19 cases across all regions by Issam AHMED Agence France Presse Johnson & Johnson’s single-dose Covid-19 vaccine has an overall efficacy of 66 percent, the company said Friday after a huge multi-continent trial, but the shot does not protect as well against a variant first detected in South Africa. Encouragingly, the vaccine was able to prevent 85 percent of severe Covid-19 cases across all geographical regions however — […]