No. In Horizon 2020, Open Access can be defined as the online access to scientific publications, at no charge to the end-user. Open Access therefore only aims at making your work as widely accessible to the public as possible – it does not aim at putting your publications in the public domain, nor to allow the public to reproduce or redistribute a work without its owner’s consent.
In other words, Open Access is only a means of dissemination and does not have any effect upon the copyright in your publications. Provided that your publications are original, they will in any case be protected by copyright.
This does not necessarily mean that you will retain the copyright in your publications: indeed, in Horizon 2020, the rule is that project results (and related intellectual property rights) are owned by the beneficiary generating them. This means that in most cases the organisation or institution you work for will have the ownership of the results, including your publications – this will usually be reflected by a clause in your employment contract. You would in any case retain at least moral rights over your work, such as the right to be identified as its author.