The user does not see the contact when adding the ContactShare

Code in Trigger:
User user = [SELECT Id FROM User WHERE Alias = 'mmana']; Contact contact = [SELECT Id FROM Contact LIMIT 1]; ContactShare contactShare = new ContactShare();
contactShare.Contact = contact;
contactShare.ContactId = contact.Id;
contactShare.UserOrGroupId = user.Id; contactShare.ContactAccessLevel = 'Edit';
insert contactShare;

Organization-Wide Defaults
Account: Private
Contact: Private

How can i solve this problem with Apex?