No, use of VWO does not have any negative impact on your website ranking.
In the case of A/B and Multivariate tests, the control and variations run on the same URL, and VWO makes changes on the fly. So any scope for content duplication, which otherwise affects SEO ranking, is nullified.
However, SEO issues may crop up when you are running a Split URL test. To avoid the issue, use query parameter rel=”canonical” in the variation URL to avoid duplicating content.
For example, in your Split URL test, there are two pages (say, http://vwo.com/A.php and http://vwo.com/B.php). When visitors land on http://vwo.com/A.php, half of them are redirected to http://vwo.com/B.php that contains some duplicate content on it.
In such a scenario where you don’t want B.php to affect your SEO, avoid content duplication. To do so, add the following code to B.php, that is, the noncanonical page:
<link rel="canonical" href="http://vwo.com/A.php"/>
While Google will index both the pages, by adding the above code, you are telling Google to use only http://example.com/A.php for SEO purposes. Here’s the link to the help page from Google’s own website: Use canonical URLs.