A study in Beijing, China was conducted on rhesus macaques and found that the monkeys were protected against subsequent infection by the identical strain of the SARS-CoV-2 virus once they entered the early recovery phase. 28 days post primary infection, researchers re-exposed the virus to four monkeys and detected no changes in viral load. Antibody titers were elevated at 14 days post re-exposure, and no viral RNA or infected cells were found in necropsy specimens following euthanasia.