Inclusion Criteria:  1. Healthy Individuals who received full vaccination with any authorized COVID-19 vaccine and decided to receive a booster vaccination as recommended by national guidelines. -  Exclusion Criteria:  Presence of diseases or therapies that are likely to interfere with the immune response to booster vaccination. Any contraindications to the vaccine planned to receive as listed in the product characteristics. Lack of willingness to undergo serial blood draws and attend follow-up appointments. Having already received a third (booster) vaccination with any COVID-19 vaccine. Women who are pregnant or breastfeeding. Persons who are not willing to sign the informed consents (biobank informed consent and study specific informed consent) -