BioNTech (BNTX 0.43%) and Pfizer (PFE 0.76%) released clinical trial results regarding the partners' experimental coronavirus vaccine program, BNT162, on Monday. Specifically, the partners published results from an early-stage German trial with BNT162b1, the most advanced candidate in a program designed to test four related vaccine candidates. 

This specific candidate delivers messenger RNA (mRNA) that leads to the production of the receptor-binding domain found on SARS-CoV-2, the virus that causes COVID-19. Results from the German study fell in line with positive results the partners posted earlier this month from a similar study run in the U.S. with an important new revelation.

Hand halting a gigantic coronavirus

Image source: Getty Images.

Coronavirus-ready T-cells 

So far, vaccine developers have been quick to report concentrations of antibodies produced in response to their vaccine candidates, but that doesn't really tell us whether immune systems are ready to mount an attack on SARS-CoV-2 the moment it shows up in the bloodstream.

BioNTech and Pfizer are making waves today because they observed high levels of CD4-positive and CD8-positive T-cell responses against the SARS-CoV-2 receptor-binding domain. In a nutshell, this strongly suggests injections primed these patients' immune systems to pounce on SARS-CoV-2 before it can cause any trouble.

This also suggests Moderna's (MRNA -3.00%) mRNA-based vaccine candidate, mRNA-1273, will have tough competition ahead. CD4-positive and CD8-positive T-cell responses were observed following injections of BNT162b1 that ranged in size from 1 microgram to 50 micrograms. While Moderna reported CD4-positive T-cell responses to its vaccine candidate, the company didn't mention the presence of CD8-positive T-cells, which are directly responsible for chewing up virally infected cells.