After 1 week of administering the Pfizer vaccine, Israel check 300 people, and 10 developed antibodies. After a second week they checked 81 people and 41 of them had antibodies.
I was surprised that if immunity is shown by day 12 or so, I would have expected pretty much everyone to have antibodies by the end of the second week. I had thought that antibodies generally are usually produced within a week of exposure to a virus or a vaccine, and I had posted that back in June:
The first time we’re exposed to a new virus, it can take 5-10 days for the B and T cells to make enough antibodies and TCR to fight this specific infection, and in the meantime, the virus has time to infect our cells and we get sick. Only as sufficient antibodies and T cells are produced do we start to recover.
https://forums.dansdeals.com/index.php?topic=116311.msg2280843#msg2280843So I looked up some numbers for the time course of antibody production in the specific case of Covid:
The earliest antibody to appear in blood is SARS-CoV-2 immunoglobulin M (IgM), usually from day 5-7 after symptoms appear, but sometimes later. Not all patients produce IgM and the amount of IgM in blood rises rapidly and falls away earlier than immunoglobulin G (IgG). ... IgG ... production follows IgM, with these antibodies detectable from day 11 and reaching a maximum 3-4 weeks after infection.
https://www.nature.com/articles/s41415-020-2228-9Most persons infected with SARS-CoV-2 display an antibody response between day 10 and day 21 after infection. Detection in mild cases can take longer time (four weeks or more) and in a small number of cases antibodies (i.e., IgM, IgG) are not detected at all (at least during the studies’ time scale). Based on the currently available data, the IgM and IgG antibodies to SARS-CoV-2 develop between 6–15 days post disease onset. The median seroconversion time for total antibodies, IgM and then IgG were day-11, day-12 and day-14 post symptom onset, respectively. The presence of antibodies was detected in <40% among patients within 1 week from onset, and rapidly increased to 100% (total antibodies), 94.3% (IgM) and 79.8% (IgG) from day-15 after onset.
https://www.ecdc.europa.eu/en/covid-19/latest-evidence/immune-responsesSo I think my mistake was that I was including all antibodies, and the Israelis probably measured the more important IgG, and those do take longer to appear. Also, the numbers I gave earlier (5-10 days) probably referred to the earliest onset of antibody production, while the median onset would be later. So considering that, the Israel report shouldn't be surprising. Also, as
@yelped suggests, it could be that antibody production takes longer in the older population they were studying, and as
@PlatinumGuy says (I think) that antibodies might be there earlier, but not detectable by our assays.
