The PC version of Vanquish launched without many issues, but since it was never designed with uncapped FPS in mind it exhibited some very strange behavior at high FPS. Most notably, players on powerful PCs found themselves taking much more damage than was expected, while also suffering from drastically reduced health regeneration.
In order to combat these problems the developers released a beta patch a couple of days ago, though due to it being a public holiday they weren't able to test it thoroughly. Now, a few days later, the fully tested update has finally arrived, and it would appear that most of the problems have been corrected! The patch notes are fairly small, so here they are in their entirety:
• Lock-on laser damage corrected for frame rate.
• Lock-on laser target lock-on timing corrected for frame rate.
• Fixed the sliding particle effect for frame rate.
• Fixed an issue where events would occasionally fail to trigger at high frame rates (e.g. the end of Act 1 Mission 6).
• Fixed animation issues when running towards the camera and firing/reloading with keyboard and mouse.
• Fixed an issue where scripted events would progress at the wrong speed at higher frame rates.
• Added “-audio 2” command line; enter the number of a specific audio device to force the game to use that rather than the default device (may help players with audio device issues).
If you've been using the beta patch for the past couple of days make sure to switch back to the standard version as otherwise you won't be able to download the new one. If you've already done so and the update is still not downloading, just restart Steam. That usually sorts it out.