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Background Serological tests directed against SARS-CoV-2 can provide information about the timing of infection and immunity against the virus. However, the kinetics of the host immune response to SARS-CoV-2 remain poorly understood. We established a household transmission study to analyze the serological responses within households, to determine longitudinal immune responses to infection. Methods From April 2020 to April 2022, we prospectively enrolled 76 households with at least one RT-PCR confirmed case of COVID-19. Participants were asked to provide blood samples at three time points: at baseline within 2 weeks of the index’s diagnosis of COVID-19, and at one- and three-months post-enrollment. Samples were tested for the presence of IgG antibodies against SARS-CoV-2 spike protein via an FDA EUA approved ELISA. Demographics, medical history, and symptomatology were also collected. Results To date, we have analyzed 238 serologic samples from 135 participants, including 82 baseline samples, 89 one-month samples, and 67 three-month samples. At baseline, 67.8% (n=40/59) of all confirmed cases tested positive for SARS-CoV-2 antibodies, which increased to 86.4% (n=57/66) at the one month, and 85.1% at three months (n=40/47). Of those confirmed infected participants that failed to seroconvert at baseline, almost all reported symptoms (n=14/19, 73.7%) and did not have chronic medical conditions (n=17/19, 89.5%). Of the 19, 3 failed to seroconvert by their third visit. All individuals who were fully vaccinated at the time of each visit tested positive for antibodies at baseline (n=26), one-month (n=27), and three-months (n=20). Of those who were not fully vaccinated, 56 (41.1%) were positive for antibodies at baseline, 62 (59.7%) were positive at one -month, and 47 (63.8%) at three-months. Differences in seropositivity rates between pediatric and adult participants, as well as between index cases and household contacts, at each visit were also identified (Table 1). Conclusion Identifying differences in seroprevalence in various demographic groups can provide insight into longitudinal immune responses post-infection. Future analyses on seropositivity among previously infected individuals who received therapeutics may be of interest. Disclosures Andra L. Blomkalns, MD, MBA, Eli Lilly and Company: Grant/Research Support Yvonne A. Maldonado, MD, Pfizer: Grant/Research Support|Pfizer: Member, DSMB, Pfizer Meningococcal Vaccine clinical trial.

Background Breath samples collected from patients infected with respiratory viruses are necessary for viral detection using breath analyzer devices. Given the highly transmissible nature of many of these illnesses, sample collection requires a multi-layered approach to ensure the safety of the research staff responsible for obtaining and transporting these samples. Our team established a protocol to minimize exposure to and transmission of COVID-19 when collecting breath samples. Methods We collected breath samples from 64 participants, of which 31 (48.4%) were positive for SARS-CoV-2 at the time of their visit. Before we started sample collection, biosafety inspection was conducted. We used a five-pronged approach to enhance safety and minimize transmission. First, we collected specimens in an outdoor space while the patients were seated in their vehicles. Second, we used a disposable mouthpiece and a one-way valve to fill a 1L TEDLAR bag. Third, patients were instructed to close the valve tightly before returning it to the staff. Fourth, we placed the bag in secondary containers which were placed in tertiary containers to minimize any contact with aerosols in the TEDLAR bag. In the last step, we placed a portable HEPA filter near the indoor sample processing unit to minimize exposure and air contamination with the samples. Study staff donned all forms of necessary personal protective equipment, including gloves, gowns, N95 respirators, and protective eyewear, during sample collection and transportation. Results A total of 64 breath samples were collected from 64 adult participants from February to March 2022. A total of 30 participants (46.9%) were within 7 days of their initial diagnosis. All participants were able to successfully collect samples without additional resources or attempts. All samples were able to be transported successfully into the lab. No staff contracted COVID-19 during the study period. Conclusion Layered safety measures, including protective equipment, physical barriers, and well-ventilated environments mitigated the risks associated with breath sample collections from infected participants. Disclosures Yvonne A. Maldonado, MD, Pfizer: Grant/Research Support|Pfizer: Member, DSMB, Pfizer Meningococcal Vaccine clinical trial.

Background Understanding how COVID-19 vaccination affects transmission of SARS-CoV-2 within households may affect policy and healthcare decisions. We hypothesized that vaccination reduces transmission and viral load in vaccinated household members. Methods We prospectively enrolled participants during March 2020 – October 2021. Index cases (IC) were eligible if they tested positive for SARS-CoV-2 within the previous 10 days and did not have household contacts (HC) who had tested positive or had symptoms of COVID-19. Participants self-collected anterior nares swabs daily for SARS-CoV-2 RT-PCR for at least 21 days, or once every member of the household had 7 consecutive negative tests. Baseline data included demographics and self-reported vaccination status. Complete COVID-19 vaccination was defined as receiving 2 doses of Moderna/Pfizer or 1 dose of Johnson & Johnson vaccine, and incomplete vaccination as receiving 1 dose of Moderna/Pfizer vaccine. Household transmission was analyzed via STATA 14.2 using logistic regression with robust standard error clustered by household, and SARS-CoV-2 cycle threshold was graphed by day of study enrollment using lowess smoothing. Results There were 60 households with positive ICs and 103 HCs for a total of 163 participants. ICs had median age 41.5 years (range 1–86) with 9 (18.0%) < 18 years. HCs had median age 34 years (range 0–87) with 32 (31.1%) HCs < 18 years. Overall, 33 (20.2%) participants received at least one COVID-19 vaccine dose. A total of 50 households had at least one HC (median 2, max 7). Transmission of SARS-CoV-2 occurred in 45 HCs (43.7%). Odds of SARS-CoV-2 transmission was lower in HCs who were vaccinated prior to study enrollment, though this finding was not statistically significant (Table 1). There were 507 positive SARS-CoV-2 tests collected among 74 participants (Figure 1). Table 1.Household Transmission By COVID-19 Vaccination Status Prior to Study Enrollment (among households with ≥ one household contact)*Using logistic regression with robust standard error, clustered by household. Reference is top group listed in each comparison (includes unvaccinated).CI: Confidence IntervalCompletely vaccinated: Received primary COVID-19 vaccination series (2 doses Pfizer or Moderna vaccine, or 1 dose Johnson & Johnson vaccine) prior to enrollmentIncompletely vaccinated: Received of 1 dose of Pfizer or Moderna vaccine prior to enrollmentUnvaccinated: No COVID-19 vaccines prior to enrollmentFigure 1.SARS-CoV-2 Cycle Threshold Over Time by COVID-19 Vaccination Status Completely vaccinated: Received primary COVID-19 vaccination series (2 doses Pfizer or Moderna vaccine, or 1 dose Johnson & Johnson vaccine) prior to enrollment Conclusion Vaccination of HCs may be protective against household SARS-CoV-2 transmission. However, analyses were limited due to low numbers of vaccinated study participants. Study enrollment is ongoing, and future analyses will include transmission during the 2022 Omicron surge, and daily symptom data which has been collected. Disclosures Yvonne A. Maldonado, MD, Pfizer: Grant/Research Support|Pfizer: Member, DSMB, Pfizer Meningococcal Vaccine clinical trial.

There is an urgent need to assess the feasibility of COVID-19 surveillance measures in educational settings.To assess whether young children can feasibly self-collect SARS-CoV-2 samples for surveillance testing over the course of an academic year.This prospective pilot cohort study was conducted from September 10, 2020, to June 10, 2021, at a K-8 school in San Mateo County, California. The research consisted of quantitative data collection efforts: (1) demographic data collected, (2) student sample self-collection error rates, and (3) student sample self-collection time durations. Students were enrolled in a hybrid learning model, a teaching model in which students were taught in person and online, with students having the option to attend virtually as needed. Data were collected under waiver of consent from students participating in weekly SARS-CoV-2 testing.Errors over time for self-collection of nasal swabs such as contaminated swabs and inadequate or shallow swabbing; time taken for sample collection.Of 296 participants, 148 (50.0%) were boys and 148 (50.0%) were girls. A total of 87 participants (29.2%) identified as Asian; 2 (0.6%), Black or African American; 13 (4.4%), Hispanic/Latinx; 103 (34.6%), non-Hispanic White; 87 (29.2%), multiracial; and 6 (2.0%), other. The median school grade was fourth grade. From September 2020 to March 2021, a total of 4203 samples were obtained from 221 students on a weekly basis, while data on error rates were collected. Errors occurred in 2.7% (n = 107; 95% CI, 2.2%-3.2%) of student encounters, with the highest rate occurring on the first day of testing (20 [10.2%]). There was an overall decrease in error rates over time. From April to June 2021, a total of 2021 samples were obtained from 296 students on a weekly basis while data on encounter lengths were collected. Between April and June 2021, 193 encounters were timed. The mean duration of each encounter was 70 seconds (95% CI, 66.4-73.7 seconds).Mastery of self-collected lower nasal swabs is possible for children 5 years and older. Testing duration can be condensed once students gain proficiency in testing procedures. Scalability for larger schools is possible if consideration is given to the resource-intensive nature of the testing and the setting's weather patterns.