The objective of this study is to determine the seroprevalence of severe acute respiratory syndrome-CoV-2 in unvaccinated sickle cell patients living in an area with high viral circulation and at risk of high viral transmission, after the 4th epidemic wave of COVID-19 in Ile-de -France, over a period of 3 months (for example, last quarter of 2021).

Sickle cell disease is a very widespread genetic disease affecting 300,000 births worldwide, with a prevalence of one affected child for 1736 births in France, the most common genetic disease in France. France is the European country with the highest prevalence of the disease while Ile-de-France is the region with the highest prevalence of sickle cell disease and COVID-19. The medical management of sickle cell patients raises many challenges related to the complexity of their disease and the comorbidities that may be associated with their conditions (arterial hypertension, pulmonary arterial hypertension, nephropathy and renal failure, cerebral vasculopathy).Our seroprevalence study will focus on the sickle cell population living in an area with high circulation of severe acute respiratory syndrome-CoV-2; it will start after the 4th epidemic wave of COVID-19 during the vaccination campaigns, in order to collect on the one hand seroprevalence data (proportion of unvaccinated seropositive sickle cell patients) and persistence of humoral immunity (quantitative) after infection in unvaccinated subjects and on the other hand, to assess the vaccination coverage in this specific population (adults and adolescents) as well as its impact (occurrence of vaccine failures).

Inclusion Criteria:

• Patient group = children with sickle cell disease:
• Children over 12 months of age and under 18 at the time of inclusion.
• Children with a major sickle cell syndrome (SS, "C gene and one sickle hemoglobin (S) gene", Sβ+, Sβ°, SE) followed in one of the centers of competence or reference for rare diseases (CRMR) "Major Sickle Cell Syndromes, Thalassemias and Other Rare Pathologies of Red Blood Cell and Erythropoiesis "from Ile de France.
• Children not subject to legal protection measures.
• Children affiliated to a French social security scheme
• Informed consent signed by one of the two parents.

Group of adults with sickle cell disease:

• Patients over 18 years of age at the time of inclusion (male, female).
• Patients with a major sickle cell syndrome (SS, "C gene and one sickle hemoglobin (S) gene", Sβ+, Sβ°, SE) followed in one of the centers of competence or reference for rare diseases (CRMR) "Major Sickle Cell Syndromes, Thalassemias and Other Rare Pathologies of Red Blood Cell and Erythropoiesis "from Ile de France.
• Patients not subject to legal protection measures.
• Patients affiliated to a French social security scheme
• Informed consent signed

Child-control group:

• Children over 12 months old and under 18 years old at the time of inclusion.
• Children without sickle cell disease
• Children monitored for asthma or with a history of asthma.
• Children not subject to legal protection measures.
• Children affiliated to a French social security scheme
• Informed consent signed by one of the two parents.

Exclusion Criteria:

• Patient group = sickle cell children :
• Infants under 12 months of age.
• Other haemoglobinopathies and heterozygous Haemoglobin AS or AC patients.
• Children already in a treatment protocol or in the exclusion period from a previous investigation.
• Children on state medical assistance

Adult sickle cell group :

• Other haemoglobinopathies and heterozygous AS or AC patients.
• Patients already on a treatment protocol or in the exclusion period from a previous investigation.
• Pregnant or lactating women.
• Patients on state medical assistance

Child control group :

• Infants under 12 months of age and adults over 18 years of age.
• Children already in a treatment protocol or in the exclusion period from a previous study.
• Children on state medical assistance