The results of early trials of the Johnson & Johnson COVID-19 vaccine are promising, and if Phase 3 trials are successful, we could soon have another tool in our pandemic toolbox to use against the virus.

Phase 1 and 2 trials of the vaccine showed it safely and effectively generated an immune response to SARS-CoV-2, the virus that causes COVID-19. That immune response was generated by a single dose, which would give it a distinct advantage over two-dose vaccines.

According to the New York Post, more than 90% of the 805 study volunteers developed neutralizing antibodies offering protection against COVID-19 in 29 days after getting a single dose of the vaccine. These antibodies remained active for 71 days after inoculation in the participants aged 18 to 55, according to the Post.

The next step, Phase 3 trials, will determine if the vaccine can safely and effectively protect a larger, randomly selected group people against infection or symptoms of the coronavirus. If effective, the new vaccine will be submitted for approval by the U.S. Food and Drug Administration (FDA).

The Johnson & Johnson vaccine works differently than the currently available drugs from Pfizer and Moderna that use genetic material called messenger RNA to train the immune system into fighting COVID-19.

According to CNN, the company’s vaccine arm, Janssen, employs a weakened version of the common cold virus called adenovirus 26. The virus carries genetic material into the body, teaching our cells to manufacture pieces of the pathogen which are then recognized by the immune system.

Researchers in the Netherlands, Belgium, and the U.S. conducted the early trials and according to their report published in The New England Journal of Medicine, the most common side effects included “fatigue, headache, myalgia, and injection-pain site.”

Johnson & Johnson said it anticipates having the results of Phase 3 trials by the end of January and if they are successful, the company will apply for emergency use authorization from the FDA.

Like other vaccine manufacturers, Johnson & Johnson has been already manufacturing the vaccine during its trials and is prepared to deliver 100 million doses if it gets a green light from the agency.