posted by jmog
My wife (had COVID late April last year) has to have minor outpatient procedures about every 2-3 months for Fibromyalgia.
Every time she has had one since COVID really got going she has to be there early for this reason. They do a COVID test AND a COVID antibody test.
Even though they KNOW she had COVID (positive test as she worked in the medical field) over a year ago.
Her COVID test comes back negative every time.
Antibody test results...
According to the CDC/FDA anything >1.0 is enough antibody to fight off a COVID-19 infection, or at least make it so mild you wouldn't really know you had it.
When they first used antibody tests as a proof of COVID cases, they were using anyone with a >1.4 as a positive case, now that is anyone >0.8.
The first time my wife had an antibody test at her hospital after having COVID her antibody test came back at 95 (point something, can't remember).
Over the last year and a couple months (she has had at least 6 tests/procedures) it has dropped down to 47.7 as of June of this year (1 year and 2 months after she had COVID).
I know this is anecdotal, but I am REALLY interested in ANY studies on a more general population of people with KNOWN COVID positive tests and at least moderate symptoms (not asymptomatic) and what their antibody levels are 6 months, 9 months, 12 months, etc after their infection.
We were made to believe that the antibodies would only last 6 months, my wifes are still WELL over the threshold to fight off COVID infection 14 months after her infection...and she didn't get the shot, so that is just from the initial infection.
She has another procedure in a couple weeks, which will put her 1 year and 5 months after infection. I will fill in where her antibodies are with the newest test I am sure she will have to have.
Antibody response reporting varies by site, lab, and test. Without knowing the units and type of measurement of the 0.8 - 1.4 numbers to which you're referring, I'm assuming that it's U/mL of the spike protein. Because of known variations from test to test, neither the FDA nor CDC has, to my knowledge, ever weighed in on how to interpret these results. The FDA certainly wouldn't; it's not within their scope. They would simply validate the use of whatever thresholds the specific test manufacturer establishes (or reject those thresholds).
There is no clinical evidence to support any claim that a certain threshold of this value is "enough antibody to fight off a COVID-19 infection". That data doesn't currently exist and probably never will. We can measure the level of circulating spike antibodies and circulating neutralizing antibodies, but using it to predict clinical response is not possible without further scrutiny in a lab.
If we're simply using anecdotes, both of my in-laws had symptomatic COVID in January and have antibody levels measured every 1-2 months for plasma donation. Both dropped to "undetectable" levels (both IgG and IgM) in July. They may still have T-cells that might mount a response if exposed, but those aren't measured by antibody tests.
There is no need for anecdotes, though. There are many studies that have examined the durability of COVID antibody response following infection, including those stratified by symptom severity. Here's the most recent high-quality study of which I'm aware: https://doi.org/10.1038/s41467-021-24979-9. This showed durable antibody response at 7 months. Here's the longest follow-up period (12 months) of which I'm aware: https://doi.org/10.1186/s12916-021-02032-2.
The duration of antibody response means nothing if we're not measuring binding activity. Coronavirus is traditionally a seasonal virus, and we have plenty of evidence that antibodies against other Coronavirus variants (pre-COVID) last 12+ months. The problem is that mutations in the virus (e.g. delta variant and beyond) may diminish the value of those antibodies.
This is, in my opinion, the most telling study available about the value of antibodies: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8369496/. They mapped out 3800 COVID variants (99.6% of all possible variants) and tested the binding activity of antibodies against the possible variants for subjects with both vaccine-induced antibodies and natural antibodies. After 3-5 months, patients who received the vaccine had antibodies with activity against 80-99% of possible variants (mean ~95%). Patients with natural antibodies had acitivity against 30-98% of possible variants (mean ~81%). So the vaccine is working against a greater portion of possible variants at 5 months, and vaccine-induced immunity is likely less susceptible to erosion by vaccine mutations.
All this to say, if your wife's antibody binding isn't measured (I recognize that there is no way for the general public to have this performed), then there's no way to determine that the antibodies which are present would even be effective against whatever variants are currently in the community.