From two to three months according to that study:
"In this study, we observed that IgG levels and neutralizing antibodies in a high proportion of individuals who recovered from SARS-CoV-2 infection start to decrease within 2–3 months after infection."
But there are a lot more scientific papers dedicated to this topic, as always DIOR, epidemiologists, scientists and oficials from the medical field are already kicking in the nuts.
ok lets handle this lttle diddy
imagine there are 5 types of antibody. some proactive, some reactive
lets just concentrate on the 2 types
the way the proactive ones work is by the antibodys surface having a wiggly outter surface. imagine it like a puzzle piece
your body has billions of different antibodies variants but lets imagine in anyone time there might be 6000 main types. always present in significant numbers 150k of each main type and then just a couple dozen thousand of less needed types.
when a virus comes in. the antibody that matches the edges of the virus joins onto it. and thus stops the virus from joining the edge of a lung cell wall.
the tail of the antibody knows it has a successful lock and then breaks the tail off to tell the body to produce more..
your body then goes from just 150k per billion. to 500milion per billion
and then when the threat is gone. it then slowly goes down to 150k numbers. and if after a few years of no seasonal attack it can go down even further to dozens
going from 500m to 150k is normal. it doesnt mean your no longer immune. it just means theres no current threat... your body can handle the residual mini battles of invaders without hassle
your body remembers and keeps a few around as a blueprint to make more when needed.
..
the best advice is to not allow millions of viral particles to invade yur body when you only have a dozen antibodies to defend
just like any battle its about numbers
if the invaders can get passed the defensive gates of the nose and throat. they can then attack the lungs
if enough are attacking lung cells then your body temperature rises as a strategy, your body floods the lungs as a strategy while it tries to create the reactive antibodies
imagine a sick person is coughing up 1million particles.
at 6inches (kissing/hugging distance) you wil take in 500k.. at 3foot(1metre) you will take in 30k and at 6 foot(2metre) you will take in 3k
so to avoid 1mill invaders standing at 2metre will only incur 3k
which is why they say 15mins at 2metre is the same as a single breath at 6inches
one breath every 3 seconds (20 a min) so 300breaths=1mill
wearing a surgical mask is 95% effective so at 6 inches 1mill instantly becomes 50k. meaning at 1metre is 1500. and 2metres is 150. so super effective
however jsut normal cloth covering is ~20% helpful
so 6inch=800k 1metre= 24k and 2metre=2.4k
thus cloth facemask is not much different than no mask.
more important is the distance
EG
cloth mask 1metre =24k
no mask 2metre=3k
distance is 7-8x better than the 0.2x mask/no mask at same distance
..
because this virus is new . people just do not have the antibody in any large number that fit the viral puzzle piece.. so they have to rely on a healthy immune system that has enough just totally random antibodies with completely random wiggly edges in the hope that by pure natural luck they have enough randomness that some fit. and then their body can produce more. and remember that these new ones are now important blueprints rather than just previously random design. and keeps enough around to easily block and create more quicker than the virus invader numbers
ive tried to dumb it down as much as possible.
think about getting 3k invaders from jsut walking passed someone for 3 seconds at 2metres
your nose and throat 12k random luck defenders kill it off. before it gets to the lungs
now imagine being 1metre and get 30k. your random luck 12k antibodies block a third. but now 18k can get into your lungs
not so bad with 20k cells per mm . and lung being 50,000mm lung surface area
its only 0.002%damage. and not really going to make your temperature rise
but getting 30k every 3 seconds on a 10min bus journey
is 0.4%. and this would increase your temperature by maybe half a degree overall
and if the reactive antibodies cant kill off them 18k that get into the lungs faster then every breath. those viruses then multiply within your body.
thus a trojan attack of invaders coming in. and invaders already inside breaking out
so again. just to be safe. stay at a distance and dont mingle for too long