Context Obesity is a pro-inflammatory metabolic state that may play a role in the development of immune-related adverse events (irAEs) associated with immune checkpoint inhibitor therapy. Objective To characterize the association between body mass index (BMI) and thyroid irAEs. Methods We performed a single center, retrospective analysis of 185 cancer patients treated with anti-PD-1/L1 from January 2014 to December 2018. Patients with normal thyroid function at baseline and available BMI were included. Main outcome measures The primary endpoint was difference in BMI in patients who developed overt thyroid dysfunction vs. remained euthyroid following anti-PD-1/L1 initiation. Additional endpoints included any (overt or subclinical) thyroid dysfunction, overt thyrotoxicosis or overt hypothyroidism, and time to development of dysfunction according to BMI. Results Any thyroid dysfunction developed in 72 (38.9%) patients and 41 (22.1%) developed overt thyroid dysfunction. Mean BMI was higher in those with overt thyroid dysfunction vs. euthyroid (27.3±6.0 vs. 24.9±4.5, p=0.03). Development of overt thyrotoxicosis vs. remaining euthyroid was associated with higher BMI (28.9±5.9 vs. 24.9±4.5; p<0.01), whereas overt hypothyroidism was not (26.7±5.5 vs. 24.9±4.5, p=0.10). Overt thyrotoxicosis developed within 57.5 (IQR 31.8-78.8) days of treatment in the low-normal BMI group, 38.0 (IQR 26.8-40.5) days in the overweight and 23.0 (IQR 21.0-28.0) days in the obese group (p=0.02). Conclusions Patients treated with PD-1/L1 inhibitors were more likely to develop thyroid irAEs, specifically overt thyrotoxicosis, with increasing BMI. Overt thyrotoxicosis occurred earlier in obese vs. leaner patients. These data highlight the complex interplay between obesity and immune response in ICI-treated patients.

Aim We evaluated the prevalence of paediatric severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infections using antibody testing and characterised antibody titres by time from exposure. Methods This was a single‐centre, prospective, cross‐sectional cohort study. Patients under 18 years old were eligible to participate if they attended the paediatric emergency department at the tertiary Shaare Zedek Medical Center, Jerusalem, Israel, from 18 October 2020 to 12 January 2021 and required blood tests or intravenous access. SARS‐CoV‐2 seropositivity and antibody levels were tested by a dual‐assay model. Results The study comprised 1138 patients (56% male) with a mean age of 4.4 years (interquartile range 1.3–11.3). Anti‐SARS‐CoV‐2 antibodies were found in 10% of the patients. Seropositivity increased with age and 41% of seropositive patients had no known exposure. Children under 6 years of age had higher initial antibody levels than older children, followed by a steeper decline. The seropositivity rate did not vary during the study, despite schools re‐opening. The findings suggest that children's immunity may start falling 4 months after the initial infection. Conclusion Immunity started falling after just 4 months, and re‐opening schools did not affect infection rates. These findings could aid decisions about vaccinating paediatric populations and school closures.