The last class of vaccines I want to discuss contain a DNA blueprint inserted into the shell of a harmless virus (usually an adenovirus vector).21 This is quite ingenious in that it uses a defective virus to deliver a message that will generate antibodies to SARS-CoV-2. These defective viruses generate immune responses but are either too weak to cause disease or are missing the necessary components to replicate altogether. In 2020, AstraZeneca, in conjunction with Oxford University, and Johnson & Johnson were two companies that had enrolled thousands of participants in trials of vaccines that
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