Objectives To improve understanding of transition from viral infection to viral clearance, and antibody response in pediatric patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Study design This retrospective analysis of children tested for SARS-CoV-2 by reverse transcription (RT) polymerase chain reaction (PCR) and immunoglobulin G antibody at a quaternary-care, free-standing pediatric hospital between March 13, 2020, and June 21, 2020, included 6369 patients who underwent PCR testing and 215 patients who underwent antibody testing. During the initial study period, testing focused primarily on symptomatic children; the later study period included asymptomatic patients who underwent testing as preadmission or preprocedural screening. We report the proportion of positive and negative tests, time to viral clearance, and time to seropositivity. Results The rate of positivity varied over time due to viral circulation in the community and transition from targeted testing of symptomatic patients to more universal screening of hospitalized patients. Median duration of viral shedding (RT-PCR positivity) was 19.5 days and time from RT-PCR positivity to negativity was 25 days. Of note, patients aged 6 through 15 years demonstrated a longer time of RT-PCR positivity to negativity, compared with patients aged 16 through 22 years (median 32 vs 18 days, P = .015). Median time to seropositivity, by chemiluminescent testing, from RT-PCR positivity was 18 days, whereas median time to reach adequate levels of neutralizing antibodies (defined as comparable with 160 titer by plaque reduction neutralization testing) was 36 days. Conclusions The majority of patients demonstrated a prolonged period of viral shedding after infection with SARS CoV-2. It is unknown whether this correlates with persistent infectivity. Only 17 of 33 patients demonstrated adequate neutralizing antibodies during the time frame of specimen collection. It remains unknown whether immunoglobulin G antibody against spike structured proteins correlates with immunity, and how long antibodies and potential protection persist.

BACKGROUND Alloantibodies against more than 50 non‐ABO blood group antigens have been implicated in hemolytic disease of the fetus and newborn (HDFN) and are expected to wane within weeks after delivery. Persistent anemia leads to the hypothesis of continued exposure to red blood cell (RBC) alloantibodies via breast milk, which has been shown in a murine model and suggested in rare case reports. CASE REPORT We report three cases of prolonged HDFN in two neonates with anti‐D HDFN and one with anti‐Jka HDFN. Patient 1 demonstrated 4+ anti‐D serologic testing beyond 2 months; therefore, antibody testing was performed on maternal breast milk. METHODS Maternal serum samples were tested for the presence of unexpected antibodies using standard Ortho gel card and 37 °C 60 minutes with anti‐human globulin (AHG) tube saline methods. Antibody titrations were performed using the standard 37 °C 60 minutes to AHG tube saline method. Fresh breast milk samples were tested using the standard 37 °C 60 minutes to AHG tube saline method for both unexpected antibodies and titration study. Fresh breast milk from an O‐positive, antibody‐negative donor was used as control for any reactivity that may have been due to milk solids or proteins alone. RESULTS Using a known methodology applied in a novel way to test breast milk for RBC alloantibodies, antibodies against fetal RBCs were identified in the maternal breast milk of three patients. CONCLUSION Maternal RBC alloantibodies are present in breast milk and may be clinically significant in patients with prolonged recovery from HDFN.

Background Patients with sickle cell disease (SCD) are frequent recipients of red blood cell (RBC) transfusions and are at risk for RBC alloimmunization. RBC alloimmunization is diagnosed by identifying RBC alloantibodies as part of pre‐transfusion testing, but this testing fails to detect alloantibodies that have evanesced. It may be beneficial to screen for new RBC alloantibody development after transfusion before possible antibody evanescence. Study Design and Methods Our institution started a new initiative for episodically transfused patients with SCD to obtain at least one antibody screen 2–6 months after transfusion as part of their clinical care. A database was created to prospectively track all transfused patients for 1 year and their post‐transfusion antibody screen results. Patients received prophylactically CEK‐matched RBC units. Results During the study year, 138 patients with SCD received a total of 242 RBC transfusions. Patients with a history of an RBC alloantibody (n = 13, 9.4%) had previously received more RBC units than non alloimmunized patients (median 11 vs. 2 RBC units, p = .0002). A total of 337 post‐transfusion antibody screens were obtained in 127 patients (92.0%) with 110 patients (79.7%) having at least one antibody screen 2–6 months post‐transfusion. With this prospective testing, two new RBC alloantibodies (anti‐C and ‐M) were identified in two patients. Conclusion It is feasible to test for new RBC alloantibody development in most episodically transfused patients with SCD as part of their routine care. The yield of this screening appears low with CEK matching, but it could still provide important information for individual patients.