LordRobin------RM t1_jdn9h1a wrote on March 25, 2023 at 5:48 PM

Reply to comment by wildfire393 in Why does tetanus vaccination lasts longer than influenza vaccination? by E-C-A

But some immunity fades even for the same strain. That was the reason for the first COVID booster. They couldn’t guarantee if would last longer than six months.

wildfire393 t1_jdnij8h wrote on March 25, 2023 at 6:52 PM

There's some dropoff over time even against the same strain, but there's also better immune response after more exposures. The first COVID shot was two doses because testing showed a better immune response for two doses at a certain concentration several weeks apart, rather than a larger dose one time.