Immunizations in Da Nang

The following is a list of vaccinations that the Canadian government recommends if you are staying in Canada (not even travelling.)  You should check your records for these:  https://www.canada.ca/en/public-health/ … tions.html

In addition the following https://travel.gc.ca/destinations/vietnam#health should be considered for Vietnam if not previously taken per the stay home schedule above: 

Hep A  (prevalent in Vietnam)
Hep B  (more difficult to contract but still prevalent)
Influenza (regular seasonal shot)
Japanese encephalitis (mosquito borne)
Measles or MMR (booster)
Varicella (chicken pox booster depending on age)
Rabies (only if your occupation may involve frequent exposure to animals)

Also consider Shingles if you are the relevant age. 

This apparently is not the case for the OP but anyone who is coming from a Yellow Fever country will require proof of vaccination for entry to Vietnam.
https://www.cdc.gov/yellowfever/maps/index.html

Some of these require boosters. In particular Hep A and B require one and two boosters respectively over six months.  If your travel plans are not urgent, you should be vaccinated in Canada simply because it will be free.  The cost in Vietnam may be reasonable but not free.