In a fresh shot of good news in the global battle against the coronavirus pandemic, Moderna (MRNA 3.06%) Wednesday reported highly encouraging preliminary results from a booster vaccine study.

The phase 2 study measured the efficacy of booster shots of the company's mRNA-1273 coronavirus vaccine. Two boosters were administered for the trial, one containing the original mRNA-1273, and another (mRNA-1273.351) specifically designed to combat the apparently more threatening South African variant of the coronavirus. In both cases, the boosters increased the body's production of neutralizing antibodies.

Also, they did so not only against the South African variant but another worrying one, the so-called Brazil variant.

The boosters were generally well tolerated, Moderna said, with most side effects being mild or moderate.

A man receiving a vaccination.

Image source: Getty Images.

They were administered to patients roughly six to eight months after the study's participants received their second shot of the two-jab mRNA-1273. The responses were measured 15 days after the booster.

"We are encouraged by these new data, which reinforce our confidence that our booster strategy should be protective against these newly detected variants." Moderna quoted its CEO Stephane Bancel as saying.

In the study, the company is also testing a multivalent booster, mRNA-1273.211, which is a combination of the other two boosters. The evaluation of this one is ongoing; Moderna said data is expected shortly.

The positive results of the trial Wednesday were overshadowed, however, by news that the Biden administration supports removing intellectual property protection from current coronavirus vaccines -- which of course includes mRNA-1273. If enacted, that could, of course, drastically reduce Moderna's revenue from its jab.

That's a key reason why Moderna stock fell by nearly 6.2% Wednesday, despite the happy news about the boosters. The S&P 500 index, meanwhile, effectively traded sideways.