This page of the guide for Resident Evil 3 Remake contains a detailed walkthrough for the puzzle that involves creating a T-Virus vaccine. The opportunity to begin this puzzle comes when you reach NEST 2. The puzzle is not difficult, although it consists of several steps.
- Where to begin the puzzle?
- How do I get two vials?
- How to produce a vaccine and complete the puzzle?
Where to begin the puzzle?
To find the vaccine making device, you need to reach floor 2F of NEST 2. First, you have to find two vials located in different rooms of Umbrella's underground lab.
An Essay on Vaccine Synthesis from the same room provides a clue as to how to solve the puzzle but reading it is fully optional.
How do I get two vials?
In the same room, interact with the computer to obtain a Flash Drive. You can carry it to level 1F and use it to open the door in the main corridor (the one with the electronic lock)
In the newly unlocked room on level 1F, there are a few zombies and two different pathways. These paths lead to two different laboratory rooms, each containing a separate vial. You can visit them in any order.
Lab 1 at Level 2F contains a Culture Sample vial.
The Incubation Lab at level 2F holds a Liquid-filled Test Tube.
How to produce a vaccine and complete the puzzle?
Go back to the room with the vaccine-making device, but don't use it yet. Open the inventory and connect the two vials together. You'll get a new item - Vaccine Base.
Now you can interact with the machine and use Vaccine Base on it.
The last part of the puzzle involves choosing the right settings for the three chambers shown on the screen. The correct setting is MID, HIGH, LOW (image above).
As a reward for passing the riddle, you'll get a Vaccine.