LONDON — British researchers first began testing the vaccine in April in about 1,000 people, half of whom got the experimental vaccine. Such early trials are usually designed only to evaluate safety, but in this case experts were also looking to see what kind of immune response was provoked.
In research published Monday in the journal Lancet, scientists said that they found their experimental COVID-19 vaccine produced a dual immune response in people aged 18 to 55.
“We are seeing good immune response in almost everybody,” said Dr. Adrian Hill, director of the Jenner Institute at Oxford University. “What this vaccine does particularly well is trigger both arms of the immune system,” he said.
Hill said that neutralizing antibodies are produced — molecules which are key to blocking infection. In addition, the vaccine also causes a reaction in the body’s T-cells which help to fight off the coronavirus.
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. Another big trial is slated to start in the U.S. soon, aiming to enroll about 30,000 people.
How quickly scientists are able to determine the vaccine’s effectiveness will depend largely on how much more transmission there is, but Hill estimated they might have sufficient data by the end of the year to decide if the vaccine should be adopted for mass vaccination campaigns.
He said the vaccine seemed to produce a comparable level of antibodies to those produced by people who recovered from a COVID-19 infection and hoped that the T-cell response would provide extra protection.
“There’s increasing evidence that having a T-cell response as well as antibodies could be very important in controlling COVID-19,” Hill said. He suggested the immune response might be boosted after a second dose; their trial tested two doses administered about four weeks apart.
Hill said Oxford’s vaccine is designed to reduce disease and transmission. It uses a harmless virus — a chimpanzee cold virus, engineered so it can’t spread — to carry the coronavirus’ spike protein into the body, which should trigger an immune system response.
Hill said Oxford has partnered with drugmaker AstraZeneca to produce their vaccine globally, and that the company has already committed to making 2 billion doses.