An advisory panel of experts in South Korea has recognized the efficacy of Johnson and Johnson's Janssen COVID-19 vaccine in the first phase of the country's vaccine approval review.

The Ministry of Food and Drug Safety said on Monday that the recognition came during a review of the results of the vaccine's phase-three clinical trial in the U.S. and seven other countries the previous day.

The efficacy rates during the trial were 66-point-nine percent 14 days after inoculation, and 66-point-one percent 28 days later.

The prevention rate dropped to 48-point-six percent after 28 days among those with underlying health conditions. As for the prevention of serious symptoms, the vaccine posted efficacy rates of 76-point-seven percent after 14 days and 85-point-four percent after 28 days.

Side effects include pain where the shot is administered, skin irritation and swelling.

The single-dose vaccine is set to undergo a second-phase review by another advisory panel on Thursday. The government's final decision is expected within the second week of April.