Evaluation of a Booster Administration of GAD-alum (Diamyd®) in Individuals With Type 1 Diabetes

Inclusion Criteria: 1. Informed consent given by patients and/or patient's parent(s) or legal acceptable representative(s) (guardian(s)) according to national regulations 2. T1D according to the ADA classification 3. Carry HLA DR3-DQ2 haplotype 4. Prior participation in either the DIAGNODE-1 or the DIAGNODE-2, having received four or three intralymphatic injections of Diamyd, respectively. 5. Females must agree to avoid pregnancy and have a negative urine pregnancy test. Patients of childbearing potential must agree to use adequate contraception, until 90 days after the administration of Diamyd. Adequate contraception is as follows: For females of childbearing potential: 1. oral (except low-dose gestagen (lynestrenol and norestisteron)), injectable, or implanted hormonal contraceptives 2. combined (estrogen and progestogen containing) 3. oral, intravaginal or transdermal progesterone hormonal contraception associated with inhibition of ovulation 4. intrauterine device 5. intrauterine hormone-releasing system (for example, progestin-releasing coil) 6. bilateral tubal occlusion 7. vasectomized male (with appropriate post vasectomy documentation of the absence of sperm in the ejaculate) 8. male partner using condom 9. abstinence from heterosexual intercourse For males of childbearing potential: 1. condom (male) 2. abstinence from heterosexual intercourse Exclusion Criteria: 1. Previous or current treatment with immunosuppressant therapy (although topical or inhaled steroids are accepted) 2. Continuous treatment with anti-inflammatory drug (sporadic treatment e.g. because of headache or in connection with fever a few days will be accepted) 3. Treatment with any oral or injected anti-diabetic medications other than insulin 4. Treatment with Vitamin D, marketed or not, or unwilling to abstain from such medication during the supplementation period 5. A history of anemia or significantly abnormal hematology results at screening 6. A history of epilepsy, head trauma or cerebrovascular accident, or clinical features of continuous motor unit activity in proximal muscles 7. Clinically significant history of acute reaction to vaccines or other drugs in the past, including Diamyd 8. Treatment with any vaccine, including influenza or Covid19 vaccine, within 1 month prior to planned study drug dose administration or planned treatment with any vaccine up to 1 month after the injection with study drug 9. Participation in clinical trials (other than DIAGNODE-1 and DIAGNODE-2) with a new chemical entity within the previous 3 months 10. Inability or unwillingness to comply with the provisions of this protocol 11. A history of alcohol or drug abuse 12. A significant illness other than diabetes within 2 weeks prior to first dosing s 13. Ongoing diagnosed or suspected post-Covid19 syndrome 14. Known HIV or hepatitis 15. Females who are lactating or pregnant (the possibility of pregnancy must be excluded by urine βHCG on-site within 24 hours prior to the Diamyd treatment) 16. Presence of associated serious disease or condition, including active skin infections that preclude intralymphatic injection, which in the opinion of the investigator makes the patient non-eligible for the study 17. Deemed by the investigator not being able to follow instructions and/or follow the study protocol