From Worms Knowledge Base
This works like a portable medipack. When activated, your worm will take some medicine and be cured of any poisons, and also recieve a hefty sum of health points. The turn ends when this medipack is used.
It's just like picking up a health crate, so this can't be difficult to implement into the game.
One might think that if it gives you a health bonus, why not use it at the very start of the game to ensure you have the maximum health just in case something big happens which you normally wouldn't survive. But this isn't the case at all. Since the health is only given to the worm who activates the Health Jab, and weapons are shared throughout the team, you may consider saving it for a specific worm if that worm is essential to victory but his health dangerously low. Also, saving the Health Jab for when your team is poisoned is a good idea as a health crates instantly cures poisons for all worms.
An important part of the gameplay in Worms is making use of crates when they arrive, as they can easily determine the outcome of a game. There is strategy and tactics involved in the capturing and guarding of a crate, and this is taken away when 'portable' crates allow players to benefit their team with no need for movement or strategical planning. This Health Boost is a debatable weapon.