The vaccine provoked a T cell response within 14 days of vaccination (white blood cells that can attack cells infected with the SARS-CoV-2 virus), and an antibody response within 28 days (antibodies are able to neutralise the virus so that it cannot infect cells when initially contracted).
The German trial included 60 healthy adults aged 18-55 years who were randomized to receive variable doses of the vaccine.
Researchers plan to prioritize testing a two-dose regimen, rather than a single shot, dampening some of the enthusiasm over the vaccine, which they've previously said they hoped to deliver as early as September.
Prof Sarah Gilbert, from the University of Oxford, UK, says: "There is still much work to be done before we can confirm if our vaccine will help manage the Covid-19 pandemic, but these early results hold promise".
While volunteers reported experiencing headaches, fatigue, muscle ache, chills, a fever, and pain at the injection site, the researchers said that none of the participants developed serious side effects following the treatment.
Last week, American researchers announced that the first COVID-19 vaccine tested there boosted people's immune systems just as scientists had hoped and the shots will now enter the final phase of testing.
Oxford has inserted genetic material from the surface spike protein of the SARS-CoV-2 virus as a way of tricking the immune system into fighting back.
Trump coronavirus briefings are coming back after new surge in cases
But with the virus on the rebound, tearing through Florida and other major states, he finds himself accused of failing to lead. He later said he had been speaking "sarcastically", although there was no evidence of this at the time.
Sars-CoV-2 is the scientific name for the coronavirus that causes the respiratory illness COVID-19. The Phase I/II data for the vaccine shows that it did not lead to any unexpected reactions and had a similar safety profile to previous vaccines of this type. So, that's why this vaccine is very promising. "Developing new vaccines is a highly complicated process and success is by no means assured", said Doug Brown, chief executive of the British Society for Immunology.
The journal said: "Authors say further clinical studies, including in older adults, should be done with this vaccine".
Speaking at a Science Media Centre, press briefing Professor Adrian Hill, director of the Jenner Institute for Vaccine Research: "Making the assumption that if natural infection doesn't give you immunity for very long therefor a vaccine won't give you immunity for very long - that doesn't follow".
He said that larger trials evaluating the vaccine's effectiveness, involving about 10,000 people in the U.K.as well as participants in South Africa and Brazil are still underway.
Both studies augur well for the large Phase III trials, where the vaccines will be tested on thousands of subjects to assess their efficacy and safety, Naor Bar-Zeev and William Moss, from the International Vaccine Access Center at Johns Hopkins Bloomberg School of Public Health, said in an accompanying editorial. "COVID-19 vaccine to overcome", study authors said.
Phase 2/3 trials of the Oxford / AstraZeneca vaccine are now underway in the UK, Brazil, and South Africa, with subsequent phase trials expected to begin in the United States in August. What if one vaccine is more effective in preventing disease in older patients and those with comorbidities who are might likely to suffer severe effects from COVID-19?
Lilly Asia Ventures, backed by US drugmaker Eli Lilly and Co, is CanSino's top shareholder, according to Refinitiv data.