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January 20, 2022 – How does the other mRNA COVID vaccine compare?

As the SARS-CoV-2 pandemic continues to evolve, we continue to get shots! This time, Spectradyne obtained a small residual sample of the other mainstream two-dose vaccine, which we’ll call vaccine #2 (see our prior blog post here describing measurements of vaccine #1). As with vaccine #1, we analyzed vaccine #2 using Spectradyne’s nCS1.

Similar to vaccine #1, and consistent with what we expect for an LNP formulation that is made more or less by mixing an alcohol phase with a lipid phase, the results show that vaccine #2 contains a broad distribution of particle sizes spanning many orders of magnitude in concentration — see figure 1.

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Figure 1. Measurements of commercial vaccine 2, plotting concentration spectral density (CSD) versus particle diameter, using two microfluidic cartridges to cover the full size range.

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Figure 2. Comparison of measurements of commercial vaccine 1 with vaccine 2.

How do the two vaccines compare? The nCS1 permits quantitative concentration measurements over any size range — see figure 2. Some slight differences between the two vaccines are detectable. In particular, vaccine #2 contains a significantly higher concentration of particles in the smaller size range, from about 65 nm – 750 nm in diameter (note the vertical scale is logarithmic, so the differences between the two distributions are quite large).

From here in the peanut gallery, can we then infer that vaccine #2 is less potent, given that a higher concentration of particles is required to elicit a sufficient immune response? Or maybe these slight differences in concentration — i.e., the dose — are responsible for the different efficacies of the two vaccines?

Rumor has it that nCS1 users in the field are preparing a broader comparison using Microfluidic Resistive Pulse Sensing (MRPS) to measure these vaccines more carefully, as well as the fundamentally different virus-based COVID vaccines. Stay tuned and we’ll point you to their results when available!

From sunscreen to liquor to the COVID vaccines, nanoparticles are all around us — let’s keep measuring!