Backgrounds:

Exhaustive reports on specific immune responses to SARS-CoV-2 in paediatric patients remain scarce, posing an unprecedented challenge to clinicians. The present study aims to characterize the SARS-CoV-2 Neutralizing antibody titer in a cohort of SARSCoV-2-infected children at different ages after 12 months of SARS-CoV-2 acute infection.

Methods

We conducted a multicenter prospective analysis of clinical record and blood samples of SARS-CoV-2 infected children at Luigi Sacco Hospital and Vittore Buzzi Hospital, Milan, Italy. From February 21st, 2020 to May 1st, 2020, subjects aged less than 18 years with a documented history of SARS-CoV-2 were included. SARS-CoV-2 neutralization assay was used to evaluate neutralizing antibodies (Nab) responses on a blood sample collected after 12 months after SARS-CoV-2 infection. Data about COVID-19 vaccination state were collected.

Results:

Seventeen children were included. Three out 17 were vaccinated at time of samples collection.

Maximum amount of Nab (1280) is found in the vaccinated subjects; no one of not vaccinated reaches similar values, whose maximum value is 320.

Nab average in our cohort is 330; this value is destinated to decrease to 90,3 if we do not consider vaccinated subjects. Higher amounts of Nab were detected in vaccinated subjects compared with not vaccinated respectively, indicating an increased humoral response after SARS-CoV-2 vaccine. No significant differences were found among SARS-CoV-2 Nab in different class ages (preschooler children, schooler children, adolescent); we found an increasing trend from younger to older, that was not maintained if we not considered vaccinated subjects.

Conclusions/Learning Points:

Our data suggest a difference in Nab according to vaccination status, in children with history of COVID-19. Correlations to class ages deserves to be further investigated in larger cohort studies.