Johnson & Johnson released a study protocol last week, describing a plan to enroll 60,000 patients across the United States for its phase III trial designed to assess the safety and effectiveness of its candidate for a SARS-CoV-2 vaccine. In this brief we compare the Johnson & Johnson, AstraZeneca and Moderna vaccines. All three companies have candidate vaccines in Phase III trials that target the S protein.
These vaccines share a common strategy of prompting the body to generate antibodies that recognize SARS-CoV-2 virus particles, surround the particles and mark them for destruction. Johnson & Johnson and AstraZeneca have used a more traditional approach. These two are created by splicing DNA for the S-protein of SARS-CoV-2 into the genome of a carrier virus. This carrier virus can infect human cells but it cannot replicate. Johnson & Johnson uses Ad26, an adenovirus, while AstraZeneca uses ChAdOx1, a chimpanzee adenovirus. The Moderna vaccine uses nanoparticles to deliver RNA encoding the S-protein. The table above summarizes the three vaccines.
The high-level view is that targeting the S-protein is likely to provide immunity against this version of SARS-CoV-2. New vaccines may be required each year and the vaccine may be more effective in some years than others. Furthermore, some vaccine approaches may be more effective in certain groups. For example, the Moderna vaccine may be safer in patients with autoimmune conditions, because it does not use a functioning virus. One barrier is that each of these candidates carry a logistical component to their success, as they all require some degree of refrigeration, which will complicate delivery and storage to areas with less infrastructure.