Those lucky few who were able to get a vaccine early on in their availability may see their validity window to enter either country close soon.
Both countries have listed the validity period expires 270 days after the date of full vaccination.
For example, if you received the second shot or single-dose vaccine in mid-January, your expiration will be mid-October.
However, both countries currently allow passengers to supplement an expired vaccine card with a negative PCR test taken within 72 hours prior to entrance.
Croatia will also accept a Rapid Antigen Test as long as it is on the list of Common RAT tests recognized by the EU member states.
These regulations indicate that many tourists will need a second dose of the one-shot J&J vaccine or the third shot of Moderna of Pfizer to enter either country soon.