I started my first bottle in December of 2019, and have been taking it since. I took it at first for a preventative, but then found out it helped my breathing, especially when I did something strenuous. Tried to get the wife to take it, but she wouldn't. She came down with Covid this past Sunday, and I still don't have it. Not saying that Quadramune is the reason, but glad I've taken it. She is now taking it too. And, I can't say enough about NanoPSA. I urinate normally, and with my prostate, that's something to say. It's even more expensive, but I've taken other suppliments for protate, and nothing works like NanoPSA. Just my opinion, but both these products work for me. Very glad I've invested here, and tried their products.