The original Resident Evil was primarily responsible for creating the term "survival horror", and although for a while it seemed like Capcom had forgotten its roots there's no denying that the company created something incredible. It's no surprise, then, that other companies tried their hand at survival horror games too - Konami quickly followed up with Silent Hill, for example.
It should be immediately obvious which game Vaccine is taking after - blocky PS1-style character models, fixed camera angles, "tank" controls, limited ammunition, a voice that says the game's title after you start; the list goes on and on.
In Vaccine you play as one of two characters trapped in a mansion. Their partner has been infected with some sort of virus and you have to find the vaccine before it's too late. What follows is essentially exactly like Resident Evil, at least at first glance. In fact, if you've played any of the classic fixed camera angle Resident Evil games this game should feel very natural.
Vaccine does bring some unique features of its own to the table, however, and they're pretty important ones - the biggest is that the layout of the mansion is entirely randomized every single time you play, changing up not only the rooms and doors, but also enemies and item locations. This essentially means no two playthroughs (or attempts at playthroughs) will be the same.
Addition number two is an experience system, which feels a little out of place at first but actually works pretty well. Dealing damage to enemies will build up XP, which can then be spent on five different stats once you have enough. "Aiming", which increases damage, is probably the most important one, but the rest shouldn't be completely ignored. After each level increase the next level for that particular stat will cost more XP, so it's good to spread the points out a little.
Time limits have occasionally been a thing in Resident Evil games (such as in most escape sequences), but Vaccine is entirely timed - you only have a limited time to find the vaccine or you lose instantly. At first this time limit is quite generous, but upon a successful playthrough you'll be able to start over with a significantly shorter period, which keeps going down further every time you win again.
While the experience system works well enough, Vaccine's two other additions - the randomization and the time limit - are cause for some major grievances. Randomization is, in theory, a neat way to add replay value to any game, but when coupled with a timer it can be the source of great frustration.
While there is always a knife in the first room (which is more useful here than it is in most Resident Evil games) finding anything else is completely up in the air. Sometimes you might find a handgun in the very next room, sometimes you might not find a handgun at all. Other times you'll come across a shotgun, while other times still you might only find proximity mines.
That's not to mention how difficult it can be to even see items sometimes - the mansion is pretty dark, so handgun clips and the like tend to blend in very well. There's no sparkle effect or anything to indicate items, so during every playthrough we dread to think how many items we're actually completely missing.
Enemy placement is similarly problematic - sometimes you'll only have to deal with simple zombies, while other times you'll be bombarded with Vaccine's equivalent of Resident Evil 2's Lickers - which take up a lot of shots to kill and hit like a freight train - and fast-moving rats, which only take one hit to kill but like to hide under places where they can't be hit until you come close enough for them to quickly scurry out and nip at your heels.
We can't quite gauge the enemy AI, either - the aforementioned Licker clones sometimes just freeze in place while you empty your entire handgun clip on them before walking back to their original location, while other times they'll relentlessly pursue you through the entire mansion, even if you run all the way back to the start. One time we were quite certain we had managed to shake one off, only for it to wander into a room miles away where we were busy fighting another one, leading to us quickly getting sandwiched between them and getting a one-way trip to the game over screen.
When you've beaten the game a few times in a row and the time limit has gotten rather low, the randomization will start to become extremely problematic in another way - running through 10 rooms only to hit a dead end and having to backtrack can waste a great deal of time, which is not good when you don't have a lot to spare. The game actually has a "true ending" unlocked by beating it about nine times in a row, though this is purely based on what we've heard from others - we certainly haven't had the luck of the gods required to do it.
One last annoyance is the abundance of spelling errors - it'd be fine if there were a few, but they're all over the place - in menus, readable notes and more. It's sloppy and reinforces negative impressions from the gameplay experience.
While Vaccine recreates the look and feel of classic survival horror games, its own additions to that formula leave a lot to be desired. Randomized games can be fun when done right and properly balanced, but Vaccine has no qualms about sometimes generating a game layout that's completely unfair and almost unwinnable, while at other times showering you with more guns and ammo than you know what to do with.
If the randomizer was more balanced and perhaps the timer or the multiple playthrough requirement for the true ending were removed, Vaccine could very well be an excellent throwback to the games that started it all - as it stands, however, it's a never-ending exercise in frustration.