3rd vaccination: "Antibody value is halved yet still effective after 3 months"

Recently NHK News on-line reported the following:

ワクチン3回目接種 ”抗体の値 3か月後に半減も一定の有効性”

2022年4月13日 21時16分

新型コロナワクチンの3回目の接種によって、感染を防ぐ抗体の値が3か月でどう変化するか、国の研究班が初めて分析結果を公表しました。抗体の値は接種直前に比べて平均で50倍以上に上昇したあと、3か月後にかけてほぼ半減したものの「一定の有効性は保たれている」としています。

厚生労働省の研究班は、3回目のワクチン接種を受けた医療従事者のうち、感染による抗体がなかった人について、変異する前の「従来株」に対する抗体の値が、3か月間でどう変化したか初めて分析しました。

このうち3回ともファイザーのワクチンを接種した440人では

▽1か月後の抗体の値は接種の直前に比べて平均で52.1倍

▽3か月後は27.5倍だったとしています。

また、2回目までファイザーで3回目にモデルナを接種した92人では

▽1か月後の抗体の値が接種の直前に比べて平均で70.3倍

▽3か月後は36倍だったとしています。

研究班の代表で、順天堂大学医学部の伊藤澄信特任教授は「3か月後にかけて抗体の値はほぼ半減したものの、水準としては高く一定の有効性は保たれている。オミクロン株に対する効果は明確に言えないが、有効性が急激に低下することは考えにくいのではないか」としています。

Translation

For the first time, a national research group published the results of an analysis on how the levels of antibodies that prevent infection would change in three months after the third inoculation of the new corona vaccine. The antibody level increased more than 50 times on average compared to just before inoculation, and then almost halved over 3 months, but "a certain level of efficacy is maintained".

According to a research group of the Ministry of Health, Labor and Welfare, among medical workers who received the third vaccination and who did not get the antibody due to infection, an analysis was done for the first time to see how the antibody value against the "conventional strain" before the mutation would change in 3 months.

Of these, 440 people who were vaccinated with Pfizer three times

▽ The antibody level after 1 month was 52.1 times on average compared to immediately before inoculation.

▽ It was  was 27.5 times after 3 months.

In addition, 92 people who inoculated Moderna for the third time, and with Pfizer up to the second time

▽ The antibody value after 1 month was 70.3 times on average compared to just before inoculation.

▽ It was 36 times after 3 months.

Suminobu Ito (伊藤澄信), a specially appointed professor at Juntendo University School of Medicine who was the representative of this research group said, "Although the antibody level has almost halved over three months, the level is high and a certain level of efficacy is maintained. While the effect on Omicron strains can't be said for sure, but it seems unlikely that the effectiveness drops sharply. "

              So, three months after the third inoculation of the new corona, the antibody level will almost drop by half.