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A coronavirus vaccine being developed by scientists at Oxford University has been shown to produce a strong immune response, according to early-stage clinical trials.   

The results, published Monday in the British medical journal The Lancet, found the vaccine developed by pharmaceutical company AstraZeneca and Oxford University generated both antibody and T-cell immune responses, which are hoped to be key to stopping an infection.  

A general view of AstraZeneca offices and the corporate logo in Cambridge, England, July 18, 2020.

“We hope this means the immune system will remember the virus, so that our vaccine will protect people for an extended period,” Andrew Pollard, lead author of the Oxford study, said in a statement released by AstraZeneca.   

The trial, part of Oxford’s Phase 2 testing, did not look at whether the vaccine actually protects against coronavirus infection, a question that will be answered in Phase 3 trials that have already begun.   

The fast pace of the vaccine effort has been cheered by officials around the world, however health experts warn that much remains unknown about the virus, and more testing is needed to understand how to offer people long-term protection against COVID-19, clinically known as SARS-CoV-2. 

“We need more research before we can confirm the vaccine effectively protects against SARS-CoV-2 infection, and for how long any protection lasts,” Pollard said.     

About 1,000 people ages 18 to 55 were involved in the Phase 2 Oxford trials, with about half of the subjects receiving the experimental vaccine.     

Scientists say immunity was detected in subjects for at least 56 days after getting the shot, but say further tests are needed to determine how long the immunity will last after that period. The experimental vaccine was shown to cause only minor side effects, including fever, fatigue and headaches. 

Screen grab taken from video issued by Britain's Oxford University, showing a person being injected as part of the first human trials in the UK to test a potential coronavirus vaccine, untaken by Oxford University in England, April 23, 2020.

Phase 3 trials of the Oxford vaccine have already begun in Brazil, South Africa and Great Britain, and will soon be expanded to the United States. These trials each involve up to 30,000 volunteers who will help scientists understand whether the experimental vaccine can really prevent people from catching coronavirus and whether it is safe. 

How long the Phase 3 trials will last depends on how high the transmission rate is in the test countries. Oxford scientists have said if the transmission rate remains high, they may be able to get enough data in a couple of months to see if the vaccine is working. But if transmission levels drop, it could take up to six months. 

The experimental vaccine is made from a weakened form of the common cold virus that has been genetically modified to carry the coronavirus’s spike protein into the body, which is believed to trigger an immune response.   

AstraZeneca has signed agreements with many governments to supply its vaccine if it is proved to be effective and granted regulatory approval. The company has already committed to making 2 billion doses. The United States has been promised 300 million doses, a European alliance has secured 400 million doses, while Britain has claimed 100 million doses.  

Britain's Prime Boris Johnson leaves 10 Downing Street to attend the weekly Prime Minister's Questions session, in parliament in London, July 15, 2020.

British Prime Minister Boris Johnson tweeted about the latest trial results Monday, 

“This is very positive news. A huge well done to our brilliant, world-leading scientists & researchers.”    

Countries around the world have also been developing their own experimental vaccines in a global race to stop the coronavirus pandemic, which has killed more than 600,000 people worldwide.     

The World Health Organization lists 23 vaccines in human tests, including the Oxford one, and 140 more in lab studies.   

Chinese researchers also published a study Monday in The Lancet of their own experimental coronavirus vaccine. The study showed modest positive results. However, some scientists have expressed concerns based on the early trials that the experimental vaccine might not work on all people because it uses a harmless virus at its core that many people already have immunity to.   

China approved the use of its vaccine for its military in June. 

U.S. drug maker Pfizer and its German partner BioNTech also reported positive progress Monday on their vaccine candidate.