Sirius Pro

Simply exclude all author posts from indexing it in SERPs. This plugin allows you to noindex posts for certain authors without modifying the code and it works with most of the available themes. Just install and activate this plugin to add noindex and nofollow meta for all author posts.
Read more about this plugin on <a href="https://siriuspro.pl" rel="nofollow ugc">WordPress</a> blog.

Noindex Author

Simply exclude all author posts from indexing it in SERPs.

mzeecedric

powtac

kikuyumoja

This plugin prevents the 404 error on author pages when the author has no posts.
It is published under the GPL 2 licence (http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt).
The original idea was taken from the the “List Authors” plugin here: http://guff.szub.net/source/custom-list-authors.php

Show authors without posts

Shows the authors page even if the author has no post.

Noindex Author vs Show authors without posts