The claim is based on the fact that AstraZeneca COVID vaccines contain an ingredient called “chimpanzee adenovirus”. 

Some social media users have jumped on the reference to chimpanzees to wrongly suggest there is a link between the vaccines and mpox, an infectious disease previously known as monkeypox. 

One Facebook post is captioned: "THE ASTRA ZENECA VACCINE CONTAINS MONKEY POX!!!!!!!!! HAVE YOU BEGAN CONNECTING THE DOTS YET ?"

Similar claims were posted to social media in 2022 and debunked by fact-checkers at both Reuters and RMIT FactLab. 

A chimpanzee adenovirus is a weakened version of a virus that causes the common cold in chimpanzees. 

The ingredient is used as a vector, which carries information into cells.

Immunology researcher Alexandra Spencer, who was part of the AstraZeneca COVID vaccine development team, told AAP FactCheck vaccine vectors are a way of sending information to the body to prompt an immune response. 

“Viruses make good vectors as they provide additional information to the immune system to indicate the protein is foreign and the body needs to mount an immune response against it,” Dr Spencer said. 

Chimpanzee adenoviruses are used, she said, because humans rarely have pre-existing antibodies that could block the viral vector from inducing an immune response.

Chimpanzee adenoviral vectors have been used in clinical trials against a variety of diseases.

 Dr Spencer said there was no truth to the claim that AstraZeneca COVID vaccines contained mpox. 

“Adenovirus and mpox virus belong to completely different classes of viruses, meaning they look and behave very differently to each other,” she said. 

Ian Jones, professor of virology at the University of Reading, told Reuters in June 2022 that chimpanzee adenovirus was “wholly different from monkeypox, and there is no possibility whatsoever that the two are linked”. 

Joshua Szanyi, from the Melbourne School of Population and Global Health, told RMIT FactLab in August 2022 that the claimed connection between the chimpanzee adenovirus and mpox was “entirely false”. 

“This viral vector [chimpanzee adenovirus] is not related to the virus that causes monkeypox,” Dr Szanyi said.

Additionally, chimpanzees are not monkeys (monkeys have tails), they’re great apes. 

Though the source of mpox remains unknown, it was discovered in 1958 in monkeys kept for research and is thought to have originated from infected rodents or non-human primates.