Japanese researchers say their analysis has found that coronavirus vaccine booster shots are still effective to a certain extent three months after vaccination.

A research team at the health ministry analyzed changes in the levels of antibodies in medical workers one month and three months after they were given booster shots.
They had no antibodies obtained from infection with the virus.

As for 440 people who received three Pfizer shots, they found that the average level of antibody one month after the booster shot was 52.1 times that seen immediately before the shot.

Three months after the shot, the average decreased to 27.5 times the level before the shot.

The antibody level in 92 people, who had received a Moderna booster shot after two Pfizer doses, was 70.3 times the level immediately before the third shot on average one month after the shot.

Three months after the booster shot, the level declined to 36 times that before the booster shot.

Juntendo University Professor Ito Suminobu headed the research team. He says although the level of antibody declined to almost half over the three months after the third shot, the level was still high, maintaining a certain extent of effectiveness.

Their analysis is about changes of antibody levels against the original strain of the coronavirus.

Ito says the effectiveness of the booster shots against the Omicron variant cannot be determined accurately, but it is unlikely that the efficacy drops drastically.