From a timeline perspective, Moderna (NASDAQ:MRNA) and Inovio Pharmaceuticals (NASDAQ:INO) are close rivals in the race to develop a vaccine for COVID-19. Moderna was the first to start human trials in March, and Inovio began its human trial less than a month later.

Both stocks have skyrocketed since the start of the year. Moderna has soared 182%, while Inovio has jumped 304% as investors bet on their coronavirus vaccine programs.

Vials of vaccine are positioned on a glass table.

Image source: Getty Images.

But which of the two is the best coronavirus stock to buy? Let's take a closer look.

The pipelines

Moderna and Inovio are both clinical stage biotech companies, meaning they haven't yet brought a product to market. Besides the COVID-19 vaccine, Moderna's most advanced product is in phase 2 testing. The company has more than 20 candidates in the pipeline for indications including influenza, Zika, and various types of cancer.

Moderna's technology involves harnessing the power of messenger RNA (mRNA). The investigational products use messenger RNA to give the body's cells instructions to make proteins that would prevent or treat disease.

Inovio has about 15 candidates in the pipeline, most of which are in phase 2 testing. The company develops medicines for infectious diseases and cancer. Inovio's lead candidate is currently in phase 3 trials for precancerous cervical dysplasia, and the company plans on reporting top-line efficacy data in the fourth quarter.

Inovio's treatments involve the use of optimized DNA plasmids. Through computer sequencing, these small circles of double stranded DNA are reorganized to produce a specific immune response in the body. Inovio then delivers these plasmids intradermally or intramuscularly through the company's own handheld smart device.

The coronavirus programs

As the U.S. government has vowed to help accelerate the development of a coronavirus vaccine, Moderna and Inovio have an opportunity to bring a product to market sooner than they would have in pre-coronavirus times. That is, if all goes well in clinical trials.

So far, Moderna is a step ahead in terms of timeline and funding. The company recently reported interim data from its phase 1 trial involving 45 healthy volunteers. Results on neutralizing antibodies, or those that stop infection, were only available for a total of eight people. In those participants, neutralizing antibodies were at or above levels of those of recovered coronavirus patients.

That is promising, but before getting too excited, we should wait to see if the trend is the same across all participants. The U.S. Food and Drug Administration gave Moderna the nod to start a phase 2 trial involving 600 participants, and a phase 3 trial is expected to start in July.

As for funding, the U.S. Department of Health and Human Services (HHS) recently granted Moderna as much as $483 million. That's enough to carry the vaccine through regulatory approval and support a scale-up in manufacturing, Moderna said.

Inovio's phase 1 study in 40 healthy volunteers is set to report preliminary data on safety and immune response in late June. The company said preclinical studies have shown "robust" neutralizing antibody and T cell immune responses. Inovio plans on beginning a phase 2/3 efficacy study in July or August if all goes well in the earlier trial.

Inovio's biggest award comes from the Coalition for Epidemic Preparedness Innovations. The global organization to accelerate vaccine development has awarded Inovio more than $17 million for its COVID-19 program.

Which stock to choose?

Moderna's and Inovio's pipelines are based on mRNA and DNA technology, respectively. That means victory in the coronavirus program not only opens the door to commercialization of a product, but also offers evidence of those technologies' efficacy in humans. That could be a big step forward for both companies.

At this stage, it's impossible to say which company will win this race to find a vaccine -- or even make it to the finish line. During clinical trials, anything can happen at any point. And share gains have been significant, pushing Moderna and Inovio prices above Wall Street's average estimates by 47% and 6%, respectively. For these two reasons, investment in Moderna and Inovio should be done with extreme caution.

That said, if I had to choose between the two biotech stocks, I would favor Moderna because it offers a bit more visibility. The company has started to deliver some human data, and so far, the results have been encouraging. And the amount of government funding is another plus, meaning Moderna may not stumble financially to bring this potential product to market.