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Antibodies for vaccinated with/without natural infection
Delta breakthrough infections elicit potent, broad and durable neutralizing antibody responses

Quote:However,  we  show  that  Delta  breakthrough  cases,  subjects  who  were  vaccinated  after  
SARS-CoV-2  infection  and  individuals  vaccinated  three  times  (without  infection)  have  
serum  neutralizing  activity  of  comparable  magnitude  and  breadth  indicate  that  multiple  
types of exposure or increased number of exposures to SARS-CoV-2 antigen(s) enhance 
spike-specific antibody responses.

Graph A shows the  level of antibodies over time (30, 60, ... days)
B, C, and D show different kinds antibodies at the same time (shortly after infection or vaccination)

A thru D are measures of how effective the antibodies were against one particular culture of COVID.
E and F are the same  graph as D but against two other cultures of COVID.

In each graph are different groups of people.  Purple triangles are vaccinated people that got Delta (so probably recently).
The cyan diamonds are people who were infected with COVID (original or other) and then got vaccinated.
The orange circles are people who have been vaccinated but not had COVID.
The gray squares are people that were infected (in WA in 2020) but not vaccinated.
The white circles are people that were not vaccinated and not had COVID.
2X means two vaccinations.  3X means three vaccinations

[Image: COVIDab-Walls.png]

Quote:Figure 1: Repeated exposures to  SARS-CoV-2 antigens through  vaccination  or infection enhance S-specific serum IgG and IgA binding titers. 

(A) Serum IgG binding titers at 30 or 60 days post infection or 10, 112, or 180 days post second or third vaccine dose were evaluated
for longitudinal samples by ELISA using prefusion-stabilized SARS-CoV-2 S Hexapro as
antigen. Serum samples were obtained from  individuals who had a Delta breakthrough infection
(n=15, magenta triangle), were previously infected then vaccinated (n=15, teal diamond), have
only  been  vaccinated  (n=15,  orange circle),  were  infected in  2020 in Washington  State  (n=15,
gray  square),  or  were  SARS-CoV-2  naive  (samples  taken  prior  to  vaccination,  n=15,  open

(B)  Serum  IgA  binding  titers  at  30  days  post  infection  or  10  days  post  second
vaccine  dose  were  evaluated  by  ELISA  using  prefusion-stabilized  SARS-CoV-2  S  Hexapro  as

© Serum IgM binding titers at 30 days post infection or 10 days post second vaccine
dose  were evaluated by ELISA using prefusion-stabilized SARS-CoV-2 S Hexapro as antigen. 

(D) Serum  IgG binding titers were evaluated by ELISA at 30 days post infection, 10 days post 
second  or  third    vaccine  dose  or  prior  to  SARS-CoV-2  exposure  (SARS-CoV-2  naive)  using  
prefusion-stabilized SARS-CoV 2P S as antigen. 

(E-F) Serum IgG binding titers were evaluated 
at 30 days post infection,  10 days post second or third vaccine dose, or prior to SARS-CoV-2 
exposure (SARS-CoV-2 naive) by ELISA using OC43 S (E) or HKU1 2P S (F) as antigen. # of 
doses:  number  of  vaccine  doses  received. 
interesting stuff!   I am vaccinated and have booster, and before leaving for airport this morning took at-home test (which I have been doing all fall before travel) and it was positive (only symptom is slightly stuffy nose).   So I am hoping this is nothing more than a tune-up for my immune system!
Good for you for taking a test before going to the airport. The US is now encouraging tests on the day of mixing in public (for unvax for public events). I haven't seen but news reports that Omicron gets virulent faster. If so, that could help explain its infectiousness. And, of course, we all hope your case remains mild.

California is again requiring masks for all people at public gatherings.

I have 2 relatives that are showing cold-type symptoms (one with fever) 2 days after attending an unmasked party. I'm wondering if there are any testing services that identify Omicron (separately from Delta). A quick look didn't show any. There are definitely tests that do, but I don't know whether if they go to, say CVS, for a test, whether that testing service's tests identify Omicron or just simply identify COVID.

Knowing nothing more than you are a "breakthrough" case, I'd guess you have a good chance that you got Omicron. CDC reports that 3% of the US cases (0.9% of California) now are Omicron. They didn't say what % of breakthrough cases are Omicron.
I took at PCR test at Walgreen's today to confirm or refute the at-home test.  Obviously from that they can determine if Omicon or Delta, but I have no idea if they will tell me.  If they do, I will post.   And my symptoms have remained VERY mild--just a slight runny nose.   

Separately, does anyone reading this board know how long after infection the PCR tests continue to show positive?   I remember something about it could be up to 90 days . . .    

(OK, I am officially guilty of thread drift)
Quote:Out of 155 American patients having undergone a PCR-based control subsequent to an initial positive finding, 88% remained positive 1 to 5 days later, and 56% out of the 105 patients tested afterwards remained positive at 21–25 days [6]. Median PCR negativation time in the 56 patients of the Chinese series by Xiao et al. was 24 days [7]. In Wuhan, 36/378 (9.5%) of patients having tested positive remained positive 30 days later, and in some cases their positivity lasted as long as 83 days [8]. The more severe the clinical presentation, the longer the duration of positivity, with a median of 31 days in a Chinese study involving 41 serious cases [9]. In a Singaporean study, 32% out of 766 COVID19 patients still remained positive at D21, 22% at D28 and 5% at D33

See also

As a reminder, initially the CDC recommended a negative test to show one is over the disease. Then they switched to 10 days after symptom onset, presumably partly because of continued positive tests.

For COVID-19 isolation recommendations, see
Much appreciated!

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