Absolutely the best we've found to boost the immune system and we've tried everything. This is the first year in over 10 that we did not get sick ... not for one day and I work with pre-schoolers every Sunday. With the very first sign of a sniffle; we doubled up and we avoided flus, colds, sinusitis and everything else my husband and I always seem to get every year - last year, I was sick for almost SIX weeks ... wish I would have known about Now's Zinc Elderberry then! :)