There are already 10 vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) in clinical trials (table), and researchers at the University of Oxford and AstraZeneca hope to have the first phase 3 data in hand this summer.
Moderna’s mRNA-1273, which entered into clinical trials just 66 days after SARS-CoV-2 was first sequenced, showcases the potential for nucleotide-based vaccines.
Like traditional live-virus vaccines, these vaccines deliver a genetic sequence into a host cell and co-opt host machinery to express antigens of interest. However, rather than using a weakened SARS-CoV-2 to transport the code, Moderna’s vaccine uses a synthetic lipid nanoparticle to carry mRNA templates.
The University of Oxford and AstraZeneca use a recombinant vaccine called AZD1222 to achieve a similar effect, engineering a chimpanzee adenovirus to carry DNA for the spike antigen.
Others are focusing on more established technologies. Sanofi and GlaxoSmithKline, two of the four top vaccine producers, are working together on a protein subunit approach. Their lead vaccine candidate consists of the spike antigen itself, combined with an immunogenic adjuvant to trigger a strong immune response.
A few companies are also focusing on whole-virus approaches, in which weakened or killed SARS-CoV-2 is used to teach the immune system what to recognize.