What We Know About the Johnson & Johnson COVID Vaccine

American multinational Johnson & Johnson said on Tuesday that it expects data from its Phase III vaccine trial "by early next week"—and that it is on track to meet its target of providing the United States with 100 million doses by the end of June.

So, what do know about Johnson & Johnson's vaccine?

First, unlike the Pfizer-BioNTech and Moderna vaccines that have already been authorized for emergency use in the U.S. and many other countries, the Johnson & Johnson jab may require only one shot.

The vaccine is currently being assessed in a Phase III clinical trial involving about 45,000 people.

While this has yet to be completed, interim data from a Phase I/IIa trial published this month in The New England Journal of Medicine revealed that the shot produced an immune response for at least 71 days, the duration of the study.

In addition, the company said in a press release that the drug was "generally well-tolerated" by the study participants—just over 400 healthy adults aged between 18 and 55.

The vaccine "induced an immune response and was generally well-tolerated across all study participants," Johnson & Johnson said. The shot induced the immune system to produce neutralizing antibodies, a type of protein that defends cells from pathogens.

"After a single vaccination, neutralizing antibodies against COVID-19 were detected in over 90 percent of study participants at Day 29 and 100 percent of participants aged 18-55 years at Day 57. These neutralizing antibodies remained stable through Day 71, currently the latest timepoint available in this ongoing study, in all participants aged 18-55 years."

The true efficacy of the vaccine will not be clear until more data from the Phase III trial is released. But the evidence so far indicates that the shot produces only "mild to moderate side effects" of the kind that are typically associated with vaccines, including fatigue, headache, muscle aches and injection site pain.

For its vaccine, Johnson & Johnson is using a modified adenovirus—a common virus that causes cold-like symptoms—to induce an immune response against the SARS-CoV-2 virus.

The adenovirus has been engineered so it does not cause any illness, while also carrying pieces of genetic material from the "spike protein" of SARS-CoV-2, which the body identifies and produces antibodies to fight.

The virus uses this spike protein to bind onto and enter human cells—a process that marks the beginning of infection.

Essentially, the vaccine prepares the immune system for the event that the body is infected with the real SARS-CoV-2 virus, boosting its defences.

Johnson & Johnson offices in California
View of the Johnson & Johnson office in Irvine, California. The company says it is on target to deliver 100 million doses of its COVID vaccine. AaronP/Bauer-Griffin/GC Images