The zoo's veterinary team determined the animals that were most at risk of contracting COVID-19 or its variants.
Those animals include orangutans, siamangs, lions and cheetahs.
The vaccinations of those priority animals and primates started last month.
Zoo officials said they are now about halfway through the list of species designated to receive a dose.
Chaffee Zoo staff members also continue safe practices, including wearing personal protective equipment around sensitive species.