Introduction:
In children, COVID-19 disease presents asymptomatically in 90’ of cases, with a 0.6’ risk of PIMS-TS; in addition, 5’ of children who are also asymptomatically infected develop Long COVID. Our weapon of defence for children under 12, as for adults, is the Pfizer-BioNTech paediatric vaccine. - and long-term undesirable effects after the complete vaccine cycle and to assess the symptomatological picture of post-vaccine infections in subjects with existing comorbidities, congenital and otherwise.

Materials and Methods:
Seventy subjects with a mean age of 8.41 years were recruited. At the time of the first vaccination session, a medical history was taken, assessing the presence of existing congenital comorbidities (cystic fibrosis, congenital heart disease, Downs syndrome, type 1 diabetes, congenital epilepsy, familial Mediterranean fever) and non congenital comorbidities. Then they were contacted by telephone at time T1 and at time T2 by submitting a questionnaire to investigate the development of undesirable effects; in addition, were assessed at four months interval T3, possible long-term undesirable effects and the acute and chronic clinical picture of those who had been infected after vaccination.

Results:
a) There were no statistically significant differences between the undesirable effects reported after the 1st dose and after the 2nd dose. b) There was no statistically significant correlation between the anamnestic data collected (pre-existing comorbidities) and the development of undesirable effects. c) None of the study subjects who became infected after vaccination developed a severe clinical picture.

Conclusions:
Following the results obtained in the cohort of affected subjects, it can be affirmed that the undesirable effects occurring after administration of the paediatric Pfizer-BioNTech vaccine are mild with a duration of no more than 24-48h and no serious reactions. The paediatric anti-Covid19 vaccine appears to be safe and effective.