The decision made last week on the acceptance of vaccinations received by Hungarian citizens abroad is governed by Government Decree 247/2021 (V.14):
From 21 May 2021, Hungarian citizens vaccinated abroad can also apply for a COVID certificate (card).
The certificate will be issued within 15 days, free of charge.
Hungarian citizens who already have a certificate can enter Hungary without quarantine at any time during the validity of the card.
You can also travel to Hungary without quarantine if you have already applied for the card online before entering and can prove it, or the purpose of the entry is to apply (which must be submitted no later than on the 2nd working day after entry).
