American pharmaceutical company Johnson & Johnson (J&J) announced on the 21st (local time) that the booster shot (boost shot) effect of the COVID-19 vaccine developed by its affiliate Janssen was strong.

J&J said that the first dose of Janssen vaccine in the United States and another dose two months later increased the preventive effect to 94% and the antibody level was also 4-6 times higher than the single dose.

In particular, J&J explained that booster shot was 100% effective in preventing severe COVID-19.

The side effects of booster shot were analyzed to be similar to those of the first inoculation.

J&J's Chief Scientific Officer, Dr. Paul Stoffels, said, "This is evidence that booster shots enhance protection against COVID-19."

The Janssen vaccine can be administered with just one administration, and its preventive effect is known to be about 66%.

The Associated Press reported that J&J's announcement was the result of an early study of 18-55 year-olds and had not yet undergone peer review.

J&J is discussing with the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) about whether or not to receive a booster shot for Janssen vaccine.