Contacts saved inside vCalendar files (.vcs) can be probably exported as separate vCard files (.vcf). This can be done using various personal manager or email clients, such as Outlook or Apple Calendar. This of course will only work if the original file contains any saved contacts in the first place.
Convert vCalendar event to vCard contacts.
We found 3 software records in the database related to .vcs to .vcf file format conversion.
Microsoft Windows software - convert vcs to vcf on Windows
An e-mail management tool distributed with Microsoft Office suite
Convert from vcs file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned vcs to vcf. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert vcs to vcf on OS X
Mac version of the popular e-mail client and personal information manager from Microsoft
Apple's personal calendar application for Mac OS X