ViraPro 3-Day Boost provides clinically studied Haschberg Austrian elderberry plus a team of other superior vitamins and minerals for amazing benefits. Haschbery Austrian Elderberry (Sambucus nigra): Clinically studied and standardized for anthocyanins, which support a strong immune response.* Vitamin A as retinyl acetate: For healthy immune system function, retinyl acetate is superior to beta-carotene.* Vitamin C: This essential nutrient is well known for immune benefits throughout the body.* Vitamin D: Research suggests that people with sufficient vitamin D levels have more robust immune systems.* Vitamin E: Included in this formula with the full family of tocopherols, vitamin E is a powerful nutrient for immune system support.* Zinc: Supports the immune activity of the thymus gland, the master gland of the immune system.* Selenium: Works with magnesium to keep the immune system healthy.* This combination, specially formulated at levels for a 3-day boost, can help you supercharge your immune system for optimal support.*