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Sanofi/GSK Vaccine Delayed Due to Poor Immunogenicity in Older Adults
The past week has seen a flurry of regulatory approvals for vaccines and mobilization of resources to begin vaccination for COVID-19. As of December 14th, Pfizer/BioNTech’s mRNA vaccine passed all emergency use evaluations and debuted in the UK, Bahrain, Canada, Saudi Arabia, Singapore, and the US, while Moderna’s vaccine is currently under FDA review for emergency authorization. The accelerated speed at which pharma companies were able to develop the vaccine bodes well for controlling the COVID-19 pandemic and ramping up resources to prevent a future outbreak. However, there are pitfalls in vaccine development, and these need to be addressed to maintain the robustness of the process. In this regard, it is important to review the vaccine candidates that fall short.
Sanofi and GlaxoSmithKline’s COVID-19 vaccine will not be available in the market sooner than the end of 2021 since their candidate failed to elicit a robust immune response in people over 50 years. The vaccine was based on a recombinant protein-coupled with an adjuvant, which is a well-established technology and deemed safer since vaccines against Hepatitis-B, HPV (human papillomavirus) have been developed using recombinant viral proteins.
The clinical data from Phase 1/2 trials showed promising results in participants aged 18-49, with neutralizing antibody titers comparable to those in patients recovering from COVID-19. However, a low immune response in older adults led the companies to rethink the concentration of antigen required for the vaccine. A recent preclinical study in primates showed that the vaccine candidate could effectively stop viral replication in the nose and lungs in 2-4 days, suggesting the vaccine is promising and needs tweaking with dosing and appropriate adjuvant.
A new Phase 2b study is scheduled to begin in February 2021 with an optimized antigen formulation while comparing the new vaccine candidate with an approved and authorized COVID-19 vaccine. They expect to have the vaccine available by the end of 2021.
This delay provides opportunities to other companies in the COVID-19 vaccine race. Johnson and Johnson announced that it would submit its adenovirus vaccine for approval in February 2021. Novavax expects Phase 3 clinical data for its protein vaccine and subsequent regulatory licenses by mid-2021.
The delay in the Sanofi-GSK vaccine slows global response against COVID-19 since their manufacturing might ensure up to 1 billion doses in 2021 and is at the heart of vaccination programs in many countries. A protein vaccine is better suited for places without access to refrigeration as compared to mRNA vaccines, which require freezing temperatures.
“We care greatly about public health, which is why we are disappointed by the delay announced today, but all our decisions are and will always be driven by science and data. We have identified the path forward and remain confident and committed to bringing a safe and efficacious COVID-19 vaccine. Following these results and the latest encouraging new preclinical data, we will now work to further optimize our candidate to achieve this goal,” said Thomas Triomphe, Executive Vice President and Head of Sanofi Pasteur. “No single pharma company can make it alone; the world needs more than one vaccine to fight the pandemic.”
By Sahana Shankar, Ph.D. Candidate
Related Article: FDA Green Lights Very First COVID-19 Vaccine in the US
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