4 official rulings from Bandai, last ruled Mar 28, 2024. Straight answers to how this card actually resolves.

If the red Tamer cards among the cards revealed from my deck do not have the [Vaccine], does that mean I can't add any cards to my hand?
No, even if it does not have the [Vaccine], you can add 1 red Tamer card to your hand. However, you can't add a red Digimon card to your hand if it doesn't have the [Vaccine].
Ruled Mar 28, 2024
This card’s effect reveals 3 cards. If the cards revealed only include either a red Digimon card with the [Vaccine] or a red Tamer card, can I still add a card to my hand?
Yes, as long as either a red Digimon card with the [Vaccine] or a red Tamer card is among the cards revealed, you can add it to your hand.
Ruled Mar 28, 2024
This card's effect reveals 3 cards. If both a red Digimon card with the [Vaccine] and a red Tamer card are among the cards revealed, can I choose to only add one of them to my hand, and place the remaining cards at the bottom of my deck?
No. This card's effect reads “Add 1 red Digimon card [...] and 1 red Tamer card among them to your hand,” so you must add as many cards to your hand as possible.
Ruled Mar 28, 2024
If both a Digimon with this card in its digivolution cards and my red Tamer are deleted at the same time, does the "gain 1 memory" effect activate?
No, it doesn’t activate.
Ruled Mar 28, 2024
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Questions and answers are Bandai's official rulings, collected and translated by the DigimonCardGame Wiki community and reused here under CC BY-SA. Card names and card text are © their respective publishers; Combalo is not affiliated with Bandai.