"All of the vaccinated monkeys treated with the Oxford vaccine became infected when challenged as judged by the recovery of virus genomic RNA from nasal secretions," Dr William Haseltine, a former Harvard Medical School professor who had a pivotal role in the development of early HIV/Aids treatments, told The Telegraph.
"There was no difference in the amount of viral RNA detected from this site in the vaccinated monkeys as compared to the unvaccinated animals. Which is to say, all vaccinated animals were infected," Dr Haseltine wrote in an article on Forbes.
The trials probing the immune response to the ChAdOx1 nCoV-19 in rhesus macaque were carried out at the National Institute of Health's Rocky Mountain Laboratory in the US, with initial results published at the end of April, reported The Telegraph.
The full trial results published last week showed the vaccine did not prevent the animals from catching the virus. However, there was signs it may reduce the severity of the infection.