This is ONLY leaving the DR to the US. Punta Cana airport....................All I can say is that none of my friends have ever mentioned it when leaving POP and no word of it until now has been posted here(?). When you are flying to the DR, a DR health statement is part of the E-Ticket.
I entered Monday, the 20th. I was not asked to show any proof of e ticket before boarding.(Jetblue from BOS) The flight attendants did announce shortly before landing that the e ticket was mandatory, and walked around to ask if anyone needed the website info. There were quite a few people off to the side before immigration, trying to fill out the form on their phone.
I was not asked for proof of vaccine on this entry, but I have been asked in the past.
And yes, the health attestation is a US requirement, that needs to be signed and turned in while checking in for departure to the US, along with proof of a negative test, and the e-ticket for departure.