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FDA Advisory Group Brainstorms Covid Vaccines

Do covid vaccines need to be adjusted to maintain vaccine efficacy and safety, and how can scientists anticipate possible mutations in time to modify existing vaccines?  Yesterday the FDA Scientific Advisory Board (VRBPAC) met virtually to discuss all aspects of Covid vaccine efficacy and development. Since the Wuhan strain was identified, variant strains developed - some like the beta and gamma variants spread locally and others like delta and omicron quickly spread across the world.  Fortunately the vaccine efficacy against severe disease and death is still above 80% and infections, hospitalizations, and deaths occur mostly in unvaccinated people.  Here are some of the issues under discussion.

1.   What is the best way to assess vaccine efficacy?  The gold standard is randomized, placebo-controlled clinical trials of thousands of volunteers - as was done in the original Covid vaccine clinical trials.  Antibodies can be measured in plasma from vaccinated subjects, but a "correlate of protection,"  i.e. that level of circulating antibodies that prevents infection, is not yet fully established.  Tests to measure memory B cells and effective T cells are too laborious for large clinical trials.

2.  The current vaccines still reduce hospitalizations and deaths, but like other viral vaccines they may not  prevent mild infection.  Is it even possible to prevent mild infections?   

See Below for 3. and 4.

FDAVRBPACapril6SIZE.jpg

3.  Can a future variant be anticipated in time to modify the current vaccines?  Or should there be vaccines developed and mixed that will cover a broader range of possible mutations in the spike protein variants that already circulated.  Some of this is being done in anticipation of further mutations.

4.  Can modified vaccines be manufactured and delivered quickly enough to prevent Covid infections and spread?  Studies are already underway to develop modified vaccines.  Influenza vaccines are mixtures of vaccines to strains that are known to be circulating, and a new vaccine (a mixture of 3 or 4 virus strains are chosen and mixed).  Modified influenza vaccines are made twice each year - once for winter in the Northern Hemisphere and once for winter in the Southern Hemisphere.  This model would be near impossible now for Covid vaccines.   

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