禁漫天堂

There are many sources providing answers about vaccine requirements to travel from Vietnam to America and later back to Vietnam, but in some respects they seem vague.聽
They state that I require
鈥淰accination certificate with QR code, digital pass via Smartphone application with QR code鈥澛�
聽 聽 聽 聽 聽 聽 聽 聽 聽 聽 聽 聽 聽 聽 or
鈥淐ovid 19 Vaccine Passport or Certificate鈥�

I have been double jabbed (August聽 2021 and Oct 2021) with AstraZeneca and I have the PC-Covid App on my Smart Phone which聽 documents this fact.聽 I no longer have the Paper Certificate as I was told that once you are digitally verifiable (in the database) you no longer require the paper copy.
My smart phone has a Vietnam phone number (SIMM).聽 I understand that my Vietnam phone number can be used to verify my vaccination, but, my Smart phone obviously will not work in the United States. I am a United States citizen with a 3 Year Temporary Residence Card. I am married to Vietnamese woman.

My questions are :聽

Q1) Do I need a 鈥淰accination certificate with QR code鈥澛� OR a聽 鈥渄igital pass via Smartphone application with QR code鈥澛� 聽OR do I need both?聽 As stated above I have a聽 鈥渄igital pass via Smartphone application with QR code鈥澛� I was told that the 鈥渄igital pass via Smartphone application with QR code鈥� would be sufficient to exit Vietnam and to return again 3 or 6 months later. , but I want to verify this prior to leaving Vietnam.

Q2) Does that PC-Covid APP work in America as well?聽 聽
Can it be used in America to validate vaccination in Vietnam?

Q3) What exactly is a 鈥淐ovid 19 Vaccine Passport鈥�?
Are they referring to my 鈥渄igital pass via Smartphone application with QR code鈥� ?

Any clarification would be greatly appreciated.聽 聽I would like to make my travel arrangements in confidence and I can not do that with these questions unanswered.
Thank you so much.

Brian