In an early-stage phase 1/2 clinical trial, BNT162b1, the COVID-19 vaccine being developed by Pfizer (PFE 0.88%) and BioNTech (BNTX -1.05%), produced antibodies against SARS-CoV-2, the novel coronavirus that causes COVID-19, after two doses.

Seven days after the second dose at the lowest two doses, 10 micrograms and 30 micrograms, 12 patients per group had antibodies capable of binding to the novel coronavirus that were 8 and 46.3 times higher, respectively, than the antibody levels of patients who had recovered from COVID-19.

More importantly, the antibodies were also able to keep the virus from infecting cells. The level of so-called neutralizing antibodies were 1.8- and 2.8-times higher than recovered patients at the 10-microgram and 30-microgram doses, respectively.

The drugmakers also tested a 100-microgram dose, but the higher dose produced unwanted side effects, so the patients weren't given a second booster shot.

Syringe drawing medicine from a vial

Image source: Getty Images.

Pfizer and BioNTech are testing four different vaccine candidates in the phase 1/2 clinical trial and plan to take the best candidate into a much larger 30,000-patient phase 2b/3 clinical trial starting as early as later this month. The companies are trailing Moderna, which is finishing up a phase 2 clinical trial for its COVID-19 vaccine, mRNA-1273, with plans to start a phase 3 study next month. But Pfizer and BioNTech's plan to run a combined phase 2b/3 clinical trial could help the duo catch up a little. 

The two companies are gearing up for production of the vaccine, with plans to manufacture up to 100 million doses by the end of this year and potentially more than 1.2 billion doses by the end of 2021.