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.

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
hexagon).  

(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
antigen. 

© 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. 

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