1935. COVID-19 mRNA Vaccination Reduces the Occurrence of Post-COVID Conditions in U.S. Children Aged 5-17 Years Following Omicron SARS-CoV-2 Infection, July 2021-September 2022

Abstract Background An estimated 1-3% of children with SARS-CoV-2 infection will develop Post-COVID Conditions (PCC). This study evaluates mRNA COVID-19 vaccine impact on likelihood of PCC in children. Methods A multi-site cohort of children enrolled 7/21/2021-9/1/2022 underwent weekly SARS-CoV-2 screening tests and were surveyed via self- or parental report 12/1/2022-5/31/2023 regarding PCC (defined as ≥1 new or on-going symptoms lasting ≥ 1 month after infection). Multivariable logistic regression was performed to estimate the occurrence of PCC by vaccination status among children aged 5–17 years whose first PCR-confirmed SARS-CoV-2 infection occurred in-study with Omicron variant, who completed the survey >60 days from infection, and who were vaccine age-eligible at time of infection per ACIP recommendations. Vaccination status was categorized as vaccinated (at least primary series completed >14 days before infection) and unvaccinated (no vaccine doses before infection). Vaccination status was verified through vaccine registry and/or medical records. Results Of 622 participants surveyed, 5% (n=28) had PCC (Table 1) and 67% (n=474) were vaccinated (Table 2). Surveys were completed a median (IQR) of 203.7 days (119.0–293.0) after infection. Children with non-Hispanic Black race/ethnicity and good/fair/poor self-rated baseline health were more likely to report PCC. Children aged 12-18 years, Non-Hispanic Asian and White children, those reporting symptomatic SARS-CoV-2 infection, and those with excellent/very good self-rated baseline health were more likely to report vaccination When comparing children with and without PCC symptoms, COVID-19 mRNA vaccination was associated with a decreased likelihood of >1 PCC symptom (aOR 0.66, 95% CI 0.43-0.99), >2 PCC symptoms (aOR 0.52, 95% 0.32-0.83), and respiratory PCC symptoms (aOR 0.53, 95% CI 0.33-0.87) (Table 3). Figure 1.Relative Risk of Post-COVID Conditions among Patients who Received Paxlovid, Ages ≥50 (N=564,303)Figure 2.Relative Risk of Post-COVID Conditions among Patients who Received Paxlovid, Ages 18-49 (N=292,818)Figure 3.Relative Risk of Post-COVID Conditions among Patients who Received Paxlovid, Ages 12-17 (N=17,178) Conclusion In this study, mRNA COVID-19 vaccination appeared to be protective against PCC in children following Omicron SARS-CoV-2 infection. The adjusted ORs correspond to an estimated 34%, 48%, and 47% reduced likelihood of >1, >2, and respiratory PCC symptoms among vaccinated children, respectively. These findings support COVID-19 vaccination for children and may encourage increased pediatric vaccine uptake. Disclosures Lisa Gwynn, MBA, MSPH, Merck: Honorari

Longitudinal parental perception of COVID-19 vaccines for children in a multi-site, cohort study

Pediatric COVID-19 vaccine hesitancy and uptake is not well understood. Among parents of a prospective cohort of children aged 6 months-17 years, we assessed COVID-19 vaccine knowledge, attitudes, and practices (KAP), and uptake over 15 months. The PROTECT study collected sociodemographic characteristics of children at enrollment and COVID-19 vaccination data and parental KAPs quarterly. Univariable and multivariable logistic regression models were used to test the effect of KAPs on vaccine uptake; McNemar's test for paired samples was used to evaluate KAP change over time. A total of 2,837 children were enrolled, with more than half (61 %) vaccinated by October 2022. Positive parental beliefs about vaccine safety and effectiveness strongly predicted vaccine uptake among children aged 5-11 years (aOR 13.1, 95 % CI 8.5-20.4 and aOR 6.4, 95 % CI 4.3-9.6, respectively) and children aged 12+ years (aOR 7.0, 95 % CI 3.8-13.0 and aOR 8.9, 95 % CI 4.4-18.0). Compared to enrollment, at follow-up parents (of vaccinated and unvaccinated children) reported higher self-assessed vaccine knowledge, but more negative beliefs towards vaccine safety, effectiveness, and trust in government. Parents unlikely to vaccinate their children at enrollment reported more positive beliefs on vaccine knowledge, safety, and effectiveness at follow-up. The PROTECT cohort allows for an examination of factors driving vaccine uptake and how beliefs about COVID-19 and the COVID-19 vaccines change over time. Findings of the current analysis suggest that these beliefs change over time and policies aiming to increase vaccine uptake should focus on vaccine safety and effectiveness

Humoral Immune Response to mRNA COVID-19 Vaccination Among Children 5-11 in a Multisite Prospective Cohort study, September 2021-September 2022

Abstract Background The PROTECT study is a longitudinal cohort study initiated in July 2021 with weekly testing for SARS-CoV-2 in four states: Arizona, Florida, Texas, and Utah. This study aims to examine the protective effect of vaccine-elicited antibody response against post-vaccination SARS-CoV-2 infections. Methods Participants, children aged 5-11, had serum collected 14-59 days after second dose of monovalent Pfizer-BioNTech COVID-19 mRNA vaccine. Vaccine-elicited antibodies were measured by area under the curve (AUC) and endpoint titer by ELISA (RBD and S2) and surrogate neutralization (SN) assays against ancestral (WA1) and Omicron (BA.2). Results Among 79 vaccinated participants, (33 [41.7%] female; median age 8.8 [SD 1.9] years), 48 (60.8%) were from Tucson, Arizona, 64 (81.0%) were non-Hispanic white, 63 (80.8%) attended school in person, 68 (86.1%) did not have any chronic conditions, 56 (72.7%) did not take daily medications; and 47 (59.5%) were infected after vaccination. Uninfected children had higher AUCs after vaccination against WA1 (p = 0.0093) and Omicron (p = 0.018). The geometric mean SN titer above the limit of detection was 346.0 for WA1 and 39.7 for Omicron, an 8.7-fold decrease (p = <0.0001). After adjustment of covariates in the WA1-specific model, we observed a 47% reduction in the odds of a post-vaccination infection for every standard deviation increase of RBD AUC (aOR: 0.53, 95% CI: 0.29, 0.97) and a 69% reduction in the odds of infection for every three-fold increase in RBD end titer, (aOR: 0.31, 95% CI: 0.06, 1.57). Conclusion Children with higher antibody levels experienced lower incidence of post-vaccination SARS-CoV-2 infection

2082. Effectiveness of Bivalent mRNA Vaccines in Preventing SARS-CoV-2 Infection Among Children Aged 5-17 years: an Evaluation of Multicenter Prospective Cohorts, United States, September 2022 - January 2023

Abstract Background The bivalent mRNA COVID-19 vaccine booster dose, composed of mRNA from ancestral and Omicron BA.4/BA.5 strains, was recommended for adolescents aged ≥12 years on September 1, 2022, and for children aged 5–11 years on October 12, 2022. However, data demonstrating the effectiveness of bivalent boosters among children and adolescents are limited. During Omicron variant sublineage predominance, September 4, 2022 – February 4, 2023, we conducted a multicenter prospective cohort study at 7 sites in the United States to assess vaccine effectiveness (VE) of bivalent COVID-19 vaccine boosters against laboratory-confirmed SARS-CoV-2 virus infection among children aged 5–17 years. Methods Participants collected weekly nasal swabs, irrespective of symptoms, and at onset of symptoms if present outside of their weekly swab cadence. Vaccination status was captured from periodic surveys (self-report), supplemented with queries from the state immunization information systems, and abstraction of electronic medical records system, when available. All respiratory swabs were tested for SARS-CoV-2 using reverse transcription-polymerase chain reaction. Symptomatic infection was defined as ≥2 COVID-like illness symptoms within 7 days of specimen collection. Cox proportional hazards models were used to estimate hazard ratios of infections comparing participants with receipt of a bivalent booster to participants without (either unvaccinated or received monovalent only), adjusting for age, sex, race/ethnicity, underlying health conditions, prior infection status, geographic site, and local virus prevalence. Results Among 3,331 participants aged 5-17 years, adjusted VE against infection was 51% (95% CI: 29–66%). When stratified by age, adjusted VE was 48% (95% CI: 15-68%) for 5-11 year old participants and 55% (95% CI: 17-76%) for 12-17 year old participants. Against symptomatic infection, adjusted VE among 5-17 year old participants was 51% (95% CI: 14-72%). Conclusion These results demonstrate that the COVID-19 bivalent booster reduces risk of SARS-CoV-2 infection and symptomatic illness among children and adolescents. All eligible children and adolescents should remain up to date with recommended COVID-19 vaccinations. Disclosures Helen Y. Chu, MD, MPH, Abbvie: Advisor/Consultant|Ellume: Advisor/Consultant|Ellume: Grant/Research Support|Merck: Advisor/Consultant|Pfizer: Advisor/Consultant|Vir: Advisor/Consultant Janet A. Englund, MD, Ark Biopharma: Advisor/Consultant|AstraZeneca: Advisor/Consultant|AstraZeneca: Grant/Research Support|GlaxoSmithKline: Grant/Research Support|Meissa Vaccines: Advisor/Consultant|Merck: Grant/Research Support|Moderna: Advisor/Consultant|Moderna: Grant/Research Support|Pfizer: Advisor/Consultant|Pfizer: Grant/Research Support|Sanofi Pasteur: Advisor/Consultant Emily T. Martin, PhD, MPH, Merck: Grant/Research Support Arnold Monto, MD, Roche: Advisor/Consultant|Roche: Honorari

Detection and Stability of SARS-CoV-2 in Three Self-Collected Specimen Types: Flocked Midturbinate Swab (MTS) in Viral Transport Media, Foam MTS, and Saliva.

Respiratory specimen collection materials shortages hampers severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) testing. We compared specimen alternatives and evaluated SARS-CoV-2 RNA stability under simulated shipping conditions. We compared concordance of RT-PCR detection of SARS-CoV-2 from flocked midturbinate swabs (MTS) in viral transport media (VTM), foam MTS without VTM, and saliva. Specimens were collected between August 2020 and April 2021 from three prospective cohorts. We compared RT-PCR cycle quantification (Cq) for Spike (S), Nucleocapsid (N), and the Open Reading Frame 1ab (ORF) genes for flocked MTS and saliva specimens tested before and after exposure to a range of storage temperatures (4-30°C) and times (2, 3, and 7 days). Of 1,900 illnesses with ≥2 specimen types tested, 335 (18%) had SARS-CoV-2 detected in ≥1 specimen; 304 (91%) were concordant across specimen types. Among illnesses with SARS-CoV-2 detection, 97% (95% confidence interval [CI]: 94-98%) were positive on flocked MTS, 99% (95% CI: 97-100%) on saliva, and 89% (95% CI: 84-93%) on foam MTS. SARS-CoV-2 RNA was detected in flocked MTS and saliva stored up to 30°C for 7 days. All specimen types provided highly concordant SARS-CoV-2 results. These findings support a range of viable options for specimen types, collection, and transport methods that may facilitate SARS-CoV-2 testing during supply and personnel shortages. IMPORTANCE Findings from this analysis indicate that (1) self-collection of flocked and foam MTS and saliva samples is feasible in both adults and children, (2) foam MTS with VTM and saliva are both viable and reasonable alternatives to traditional flocked MTS in VTM for SARS-CoV-2 detection, and (3) these sample types may be stored and transported at ambient temperatures for up to 7 days without compromising sample quality. These findings support methods of sample collection for SARS-CoV-2 detection that may facilitate widespread community testing in the setting of supply and personnel shortages during the current pandemic