Mucosal Immunity Against SARS-CoV-2 Infection in COVID-19 Patients

diagnostic specimens via nasopharyngeal swab and throat swab were collected following the current standard operating procedures.

MLF will be collected via nasal absorption at the inclusion visit by study staff and four more time points by the parents or by the children themselves. Nasal absorption is performed by maneuvering a strip of synthetic absorptive matrices (SAM) into the lumen of the nostril, avoiding rubbing against the nasal mucosa. The outside of the nose is then pressed with a finger to cause apposition of the SAM against the mucosa.

Participants will be asked to wash their hands with soap and warm water. The procedure involves cleaning the ball of the fingertip with an alcohol swab, then using a sterile disposable lancet to pierce the skin (BD Microtainer Lancet or similar). The lancet is placed in a spring-loaded device, which propels the lancet a fixed distance (a few mm) into the skin when the trigger is pressed. Approximately 10-20 drops of blood (0.3 ml) will then be collected with a sterile capillary tube. The participant is given a cotton wool pad to mop up any extra blood, and an elastoplast-type bandage is placed over the finger if necessary. Fingerprick blood samples will only be collected from participants older than 6 months at 28-32 days after the first home visit (d0). Lancet length will be adjusted for age (2.0 mm for participants 8 years and older, 1.5 mm for participants older than 6 months and younger than 8 years).