Johnson & Johnson (J&J) pharmaceutical company subsidiary Janssen launched its new late-stage trial for its experimental COVID-19 vaccine on Monday.

J&J's COVID-19 vaccine candidate is a two-dose regimen. Half of the volunteers will be given both doses with around two months apart.

Janssen already has an ongoing large-scale trial in which only one COVID-19 vaccine dose was given to the volunteers, said a BBC report.

The drugmaker will need thousands of volunteers as J&J expands its trials by geography and type, said a report from Reuters.

The study is looking to recruit 6,000 volunteers in the UK then will move globally where it will have a total of 30,000 volunteers.

Volunteers will be recruited across 17 different sites in the UK to participate in the development of the experimental shot, currently called Ad26COV2.

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The announcement came a week after preliminary results showed Pfizer's COVID-19 vaccine provided more than 90% protection against the virus.

Janssen's COVID-19 Vaccine

A harmless cold virus was used in the development of the shot.

Scientists said it will deliver the spike protein of the coronavirus into the body, which will hopefully prompt an immune response, reported Associated Press.

Volunteers will be given either a placebo of saline or the experimental shot with the said components.

Fifty seven days later, they will then be given a second dose or another placebo, said Dr. Saul Faust, who is helping lead the study.

"It's fantastic news that vaccines aimed at the spike protein can prevent coronavirus disease," he said at a news briefing.

He added that while they are optimistic, researchers still don't know how each of the vaccines will behave once given to the volunteers.

Faust also said the length of time for which the vaccine can give immunity is still unknown.

J&J Vaccine Trials

The researchers are hoping to get a diverse set of volunteers for their trials.

Particularly, they are looking forward to having those disproportionately affected by the disease on-board. These groups include older people and those from ethnic minorities.

It's important to get a diverse pool of volunteers since different people have varying reactions to certain medications.

For example, the Pfizer and BioNTech vaccine may have some global excitement linked to it but it is still unknown how well it works for the elderly and for how long the immunity it provides may last.

Finding a safe and effective COVID-19 vaccine in a matter of months has been a struggle for the drug making industry.

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For that, it is best to look at different approaches to fight off the virus.

Some vaccines may be effective for different ages and one company may not be enough to offer immunity for the whole globe.

"It is really important we pursue many different vaccines from many different manufactures," said Faust.

Janssen said if the results if the results of the single-shot trial are promising, they may simplify the distribution of their vaccine compared to other rivals that are also looking into a double-dose vaccine.

The efficacy of double-dose vaccines could be affected if someone misses their second shot.

The UK trial scientists did not offer further details as to what other countries may be involved in the two-dose trial, but they assured the Britain won't be the only place it will conduct studies.

Recruitment is expected to be complete by March 2021 and the trial will end after 12 months.