A correlate of protection for #SARS-CoV-2 vaccines is urgently needed | Nature Medicine
▻https://www.nature.com/articles/s41591-021-01432-4
À propos de deux études qui ont cherché s’il y avait une corrélation entre #anticorps, notamment neutralisant, et #protection.
L’utilité d’un titre seuil est discuté.
The results from both teams showed a significant correlation between vaccine efficacy and vaccine-induced neutralizing antibody activity. Even titers of binding antibody (e.g., as measured by enzyme-linked immunosorbent assays, which are much easier to perform at large scale than neutralization assays are) seemed to correlate well with efficacy4.
These findings suggest that antibodies may provide a correlate of protection, with further support for this coming from animal studies12 and natural-infection cohorts13.
Relying on a correlate of protection— although extremely helpful in many ways— also comes with certain risks. Although certain correlates can be non-mechanistic , meaning an immune marker that indicates protection but does not cause it, antibodies are often mechanistic correlates of protection, especially if they are capable of neutralizing the pathogen in question.
Correlates may be specific to a vaccine platform or even specific to a vaccine. Some vaccines may be highly protective but may not induce the type of immunity established as a correlate and, vice versa, a vaccine may induce the immune response used as correlate but may still not provide protection, especially when a non-mechanistic correlate of protection is used. Nevertheless, robust preclinical and clinical studies make these scenarios unlikely; vaccine developers understand the type of immunity their vaccines induce, and animal experiments12 (and monoclonal antibody therapeutics in humans) show that antibodies do directly participate in protection (and therefore are probably a mechanistic correlate of protection)
A more robust threshold of protection, based on data from individual people instead of pooled efficacy data, can be derived from breakthrough cases in phase 3 studies and observational studies. Therefore, swift data sharing and collaboration to establish an absolute correlate of protection should be the number one priority for vaccine producers, academic researchers and regulatory agencies. Although it is unlikely that such an effort will arrive at a flawless absolute correlate that can be applied to all vaccine candidates, all viral variants and all patient populations, it would certainly be extremely helpful in catalyzing the licensure of more vaccines, guiding patient management and informing public-health decisions.
