How long will Covid antibodies show up on tests?

[Spryte]

Do we have any idea how far out antibodies are showing up on blood tests?  
 

Are these the same antibodies that would show up if a person had the vaccine in the meantime?

 

 

[Terabith]

No, not the same antibodies that show up if you get the vaccine.  Vaccines mostly train T-cells.

It seems like it varies.  Anywhere from "never develop antibodies that show up on tests" to a year out.  

[Spryte]

Thanks!

[Pam in CT]

FWIW my husband, whose career has been medical / pharma adjacent, was 100% CERTAIN I'd had COVID back in late Feb 2020 -- I'd spent an unplanned 18+ hour layover in SFO jam-packed with other unexpectedly laid-over passengers, and 5 days later was flattened for 3 days with flu-like symptoms although I'd had the flu shot.

But at his urging, because he was so absolutely convinced, I got antibody-tested the day before I got Moderna 1 (March 2 2021, so just about exactly a year after he was sure I had had it), and had no antibodies.

 

(As a matter of science, this proves exactly nothing, LOL)

 

 

 

 

[AbcdeDooDah]

My sister is 6 months out from Covid. She has given blood twice since then. The antibodies did not show in her first donation but did show up in her second, about 5 months out. FWIW.

[bluemongoose]

I have a relative that had COVID symptoms, but before her area was testing. She has heart troubles now that she never had before. They did an antibody test about 9 months afterward and she didn't show antibodies. They still suspect COVID though, based on long term issues.

[Penelope]

I don’t know about how often they will show up on blood tests that the general public has available to them. 
In one of the studies out of an immunology lab where they are following people over months and testing for multiple responses of the immune system, the last one that was published showed strong responses at eight months at levels that suggest they would last for a very long time. That was months ago, and I don’t know if there is an update yet.

So this is the latest I heard on antibody tests.There are different antibody tests available, possibly different levels of accuracy. And some test for spike (S) protein antibodies, while some test for N-protein. The vaccine result only in antibodies to to spike. If you get a test that only shows those antibodies and you were vaccinated, you can’t tell whether the antibodies are due to vaccine or to natural infection. If you were naturally infected and developed antibodies, it should be to both S and N. 
 

So once you’ve been vaccinated, the only way to tell if you were also infected and developed antibodies from that would be to get a test for the N antibodies.

Edited May 20, 2021 by Penelope

[Spryte]

This is helpful, thanks.

We have had a small suspicion that we may have had it before testing was available, when DH brought something home from from a large conference overseas. Whatever it was, it was ugly.  Like 6 weeks of nebulizer treatments and misery for some of us.  I’m not convinced, but maybe.

We all reacted worse to the first Pfizer shot than the second.

And ... our DO does OMT. (If anyone has heard of that... It stands for osteopathic manipulation therapy, I think?) She treated DS yesterday and asked if he’d had it.  Something she was finding was consistent with things she only sees in people who have had Covid. Just made me wonder again.

Edited May 21, 2021 by Spryte

[lulalu]

At the beginning of the month I was tested at a local university as they are studying this. 14 months out for me and I still have antibodies. 

 

[bethben]

I’m not sure how long anti-bodies stick around in the blood, but the absence of them does not show that you have lost immunity.  You are looking long term for T-cells.  They did studies on people who had SARS back in the early 2000s.  They were showing immunity to the current Covid-19 18 years later.  

[Farrar]

As I understand it, you'll probably never know for sure. Which is cruddy.

[Halftime Hope]

There are t-cell tests available to the public now, approved by the FDA under an EUA.  That's what I'd do if I really, really wanted to know. 

[KSera]

13 minutes ago, Halftime Hope said:

There are t-cell tests available to the public now, approved by the FDA under an EUA.  That's what I'd do if I really, really wanted to know. 

I’ll have to look into this. I figured I’ll just never know if what I had in March 2020 was Covid. I don’t really have a good justification at this point other than curiosity, though. My doctor tested my antibodies in October, because I had enough going on that could have been post-Covid stuff, but that was negative. That was almost 6 months after I was sick. 

[Halftime Hope]

2 minutes ago, KSera said:

I’ll have to look into this. I figured I’ll just never know if what I had in March 2020 was Covid. I don’t really have a good justification at this point other than curiosity, though. My doctor tested my antibodies in October, because I had enough going on that could have been post-Covid stuff, but that was negative. That was almost 6 months after I was sick. 

https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-adaptive-biotechnologies-t-detect-covid-test  

The company claims 99.8% specificity. Time will tell how long the t-cell response lasts, although it should be a long, long time.  

[KSera]

9 minutes ago, Halftime Hope said:

https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-adaptive-biotechnologies-t-detect-covid-test  

The company claims 99.8% specificity. Time will tell how long the t-cell response lasts, although it should be a long, long time.  

I’m trying to see how this might be affected by vaccination, and so far I can’t find anything that addresses that. 

[Spryte]

33 minutes ago, Halftime Hope said:

https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-adaptive-biotechnologies-t-detect-covid-test  

The company claims 99.8% specificity. Time will tell how long the t-cell response lasts, although it should be a long, long time.  

This is interesting, thanks.  I wonder if we can ask our GP to run this one, or if it’s easily available yet.

[wathe]

Re T-Detect referenced upthread: 

It looks like the clinical sensitivity was tested at 0-7, 8-14, and >= 15 days post symptom onset, and also a second, larger data set post positive PCR  test with the same time intervals.

Prospective clinical specificity, which relates to rate of false positives, was very high at 98.7

Clinical sensitivity, which relates to false negatives, was somewhat lower: for >= 15 days post symptom onset sensitivity was 92%, with 95% confidence interval 78-98%, and for >=15 days post positive PCR sensitivity 97.1%, with 95%CI 92-99%.

It looks like >= 15 days post positive PCR test is the longest sensitivity time frame reported.  That might not very long at all?  I'd be interested to know what the upper bound was; ie were any of the study subjects significantly more that two weeks post acute illness or not?

It will be interesting to see how well real world data correlate

Sensitivity and specificity data are on pages 8-10

[wathe]

 

1 hour ago, KSera said:

I’m trying to see how this might be affected by vaccination, and so far I can’t find anything that addresses that. 

From the FDA EAU authorization summary:

13. The performance of this test has not been established in individuals that have received a COVID-19 vaccine. The clinical significance of a positive or negative result following COVID-19 vaccination has not been established, and the result from this test should not be interpreted as an indication or degree of protection from infection after vaccination.

Along with a bunch of other CYA disclaimers on the last page basically saying that a positive test may not mean past covid infection and a negative test may not mean absence of past covid infection, and the test should not be used to make clinical decisions..........

ETA link

Edited May 22, 2021 by wathe

[KSera]

8 minutes ago, wathe said:

From the FDA EAU authorization summary:

13. The performance of this test has not been established in individuals that have received a COVID-19 vaccine. The clinical significance of a positive or negative result following COVID-19 vaccination has not been established, and the result from this test should not be interpreted as an indication or degree of protection from infection after vaccination.

Along with a bunch of other CYA disclaimers on the last page basically saying that a positive test may not mean past covid infection and a negative test may not mean absence of past covid infection, and the test should not be used to make clinical decisions..........

Thanks. That’s enough for me to decide it wouldn’t be worth seeking out in my case. Unless/until we hear otherwise, T cell response seems like it would be hard (impossible?) to detect the difference between vaccine-induced or disease-induced T cells response. Maybe this would be useful for someone with a compromised immune system to know if they mounted a protective response to the vaccine?

[Spryte]

2 hours ago, KSera said:

Thanks. That’s enough for me to decide it wouldn’t be worth seeking out in my case. Unless/until we hear otherwise, T cell response seems like it would be hard (impossible?) to detect the difference between vaccine-induced or disease-induced T cells response. Maybe this would be useful for someone with a compromised immune system to know if they mounted a protective response to the vaccine?

Yes, I’m thinking it’s not worthwhile.  Though DS is immune compromised with a ton or risk factors, as am I, so there would be some value in knowing if we’d had it.  Doc seems to think it a possibility.

I’m always inclined to think we had some other vile, vicious bug, but we likely won’t ever know for sure. Whatever it was, it made us all much more cautious because none of us wanted to be that horribly ill again.