What makes the Novavax vaccine different from the others?
With the first month of lockdown 2021 coming to an end, the news of another promising vaccine, Novavax, has been announced with positive statistics in phase 3 trials. The UK has ordered 60 million doses of this but how exactly does it differ from the existing vaccines?
The Pfizer and Moderna vaccines contain an mRNA coding sequence to instruct our cells to construct the SARS-CoV-2 spike protein, which our immune system will later recognise as foreign. In comparison, Novavax (NVX-CoV2373) have focused on inserting the spike gene into insect cells to manufacture large quantities of the protein, that will then be extracted and used for the vaccine. The company have also included another viral protein, Matrix, as an adjuvant that helps to enhance the immune response and produce more neutralising antibodies.
Alternatively, there is the Oxford Astrazeneca vaccine that uses a live, but weakened, chimpanzee Adenovirus (responsible for the common cold) that acts a carrier for the SARS-CoV-2 spike protein. This method is promising because this relies on the virus as a tool to express this antigen in high quantities for the immune cells to detect but the virus has been engineered so that it cannot infect and cause disease.
Despite the differences in the design of the vaccine, all of them share a primary objective: trigger immune cells to start producing antibodies and develop immunological memory for future encounter. mRNA vaccines have become more popular than the traditional vaccine as they are faster to process since the production of proteins for vaccines require purification and sometimes modification. Furthermore, due to the fact that mRNA resides in the cytosol, there is no concern that this will integrate into our own genome, as well as the fact that this is quickly broken down once translated to build the protein.
Another major difference between these types of vaccines is the temperature in which they need to be stored at, mRNA is sensitive to degradation, meaning that Moderna requires storage at -20 degrees whilst Pfizer needs to be maintained at -70 degrees to remain stable and effective for delivery. Because the Novavax and Oxford Astrazeneca jabs are not has sensitive to degradation, these have a temperature advantage in that it can be kept and transported in the fridge.
Reports following the phase 3 clinical study stated that Novavax will be undergoing assessment after demonstrating 85.6% efficacy against the UK variant strain, and 95.6% against the original strain amongst 15,000 participants. The phase 2 clinical trial tested this against the South African variant, that is currently of great concern, showed 60% efficacy; despite this, it is the first vaccine to show efficacy against all variants of SARS-Cov-2. Another phase 3 trial is underway to further study the safety and protection conferred but this continues to provide hope as the principal investigator, Shabir Maddi said: “I am encouraged to see that Novavax plans to immediately begin clinical development on a vaccine specifically targeted to the variant, which together with the current vaccine is likely to form the cornerstone of the fight against covid-19”.
