The results of the Phase I/II trial published on July 20, 2020 in the scientific journal, The Lancet, indicate no early safety concerns and shows strong immune responses in both parts of the immune system. The results from these trials have demonstrated that both groups have taken the next step towards the discovery of a safe, effective, and accessible vaccine against coronavirus. 

Andrew Pollard and colleagues from Oxford report their phase 1/2 randomized trials of one injection of chimpanzee adenovirus-vectored COVID-19 vaccine. Their study ran from April 23 to May 21, 2020, 1077 healthy adults (50% male, 90.9% white) were recruited from five centers in the UK, and were followed up with after 28 days. While Wei Chen and colleagues from China reported results from phase 2 randomized trials of one injection of non-replicating adenovirus-vectored COVID-19 vaccine.  

Both studies report local and systematic mild adverse symptoms such as fever, fatigue, and injection site pain, no severe adverse events are reported. The Ad5-vectored COVID-19 vaccine from the Chinese team is safe and induced a significant immune response in most recipients after a single immunization. ChAdOx1 NCoV19 from Oxford was reported safe and increased antibody responses. The results from both studies support large-scale evaluation of these candidate vaccines in an ongoing phase 3 program, where the vaccines must be tested on much larger populations of participants to assess their efficacy and safety.