Vaccinations are an important part of keeping dogs and cats healthy. Here is an overview of the necessary vaccinations for dogs and cats, as well as the possible side effects:

Necessary vaccinations for dogs
DHPP (distemper, hepatitis, parvo and parvo)

Side effects: fever, fatigue, vomiting, diarrhea, new allergic reactions (rare).
Rabies

Side effects: local reactions at the injection site, fever, allergic reactions.
Leptospirosis

Side effects: fever, loss of appetite, allergic reactions.
Bordetella (kennel cough)

Side effects: fever, cough, allergic reactions.

Necessary vaccinations for cats
FVRCP (Feline Viral Rhinotracheitis, Calicivirus, Panleukopenia)

Side effects: fever, fatigue, local reactions at the injection site.
Rabies

Side effects: local reactions at the injection site, fever, allergic reactions.
FeLV (Feline Leukemia Virus)

Side effects: swelling at the injection site, fever, allergic reactions.

Summary
It is important to consult a veterinarian to determine the required vaccinations based on your pet's age, health and background. In addition, the pet should be monitored after vaccination and any unusual phenomenon should be reported to the veterinarian.