Why manufacturing Covid vaccines at scale is hard
The first Covid-19 vaccine candidate went into the arms of volunteers in Seattle in March 2020. It was an mRNA vaccine from Moderna. The mRNA candidate from BioNTech and Pfizer followed in April. By December 2020, these two had become the first vaccines to be approved by the US Food and Drug Administration (FDA). Hot on their heels are rivals based on adenovirus vectors from AstraZeneca and Johnson & Johnson, as well as Sputnik V from Russia.