A vaccine developed in China appears to be safe and may protect people from the new coronavirus, the researchers reported on Friday.
The initial stage trial, Published in The Lancet, it was conducted by researchers from various laboratories and included 108 participants between the ages of 18 and 60. Those who received a single dose of the vaccine produced certain immune cells, called T cells, within two weeks. Antibodies required for immunity peaked at 28 days after inoculation.
"These are promising data, but they are initial data," said Dr. Daniel Barouch, director of vaccine research at Deaconess Beth Israel Medical Center in Boston, who was not involved in the work. "Above all, I would say this is good news."
The trial is the first step in testing the vaccine and its main purpose was to verify its safety. Proof of its effectiveness will require testing on thousands, perhaps hundreds of thousands, more people.
A vaccine against the new coronavirus is considered to be the best long-term solution to allow countries to reopen their economies and return to normal. Various teams around the world compete to test multiple candidates.
The results of another human vaccine trial have been published in a scientific journal. That vaccine has now entered human trials mid-stage, the manufacturer, Sinovac Biotech Ltd., said on Friday.
The vaccine reported today was made with a virus, called Ad5, modified to carry genetic instructions to a human cell. The cell begins to produce a coronavirus protein; the immune system learns to recognize the protein and attack it, in theory preventing the coronavirus from gaining a foothold.
But Ad5 is a cold virus that many people have probably already been exposed to. About half of the participants in the trial had strong antibodies to Ad5 before receiving the vaccine.
In these people, "their immune systems will essentially lift and mitigate the effect of the vaccine," said Dr. Kirsten Lyke, a vaccinologist at the University of Maryland who is leading another coronavirus vaccine trial.
Researchers in China found that people who had Ad5 antibodies were less likely to develop a strong immune response to the vaccine.
"That may limit the use of this vaccine," said Dr. Peter Hotez, dean of the Baylor College of Medicine's National School of Tropical Medicine. "If you're comparing vaccines, adenovirus vaccines so far appear to be on the lower end of the spectrum."
Other teams have turned to adenoviruses to develop coronavirus vaccines, but are using less common strains, or even animal strains, to get around this problem. Dr. Barouch, who is working on an Ad26 vaccine, said his team has data from Africa and Southeast Asia that show that people generally don't have high levels of antibodies against that strain.
Only a subset of people in the new trial produced neutralizing antibodies against coronavirus, the type of molecule necessary for immunity. Other candidate vaccines have reported better results in neutralizing antibody levels.
People aged 45 to 60 also produced weaker immune responses after vaccination than younger participants. Dr. Lyke said the responses may be even weaker among people over the age of 60.
"That is a very important target population that they would have to examine," he said. Dr. Lyke suggested that this vaccine may be more suitable for younger populations and children.
The results are based on data from a short period and it is unclear how long protection from the vaccine could last.
The researchers tested three doses and said that the highest dose appeared to be the most effective. This dose response is encouraging, experts said. But people who received the highest dose also experienced most of the side effects.
According to experts, about 80 percent of the participants reported at least one side effect, all expected with a viral vaccine. In addition to pain at the injection site, about half of the participants reported fever, fatigue, and headaches, and about one in five had muscle pain.
The experts praised the researchers for publishing all of their data for others to review, and said the results were generally promising.
"What we hope is that there will not be one vaccine but several vaccines that will be approved," said Dr. Barouch. "The world needs multiple vaccines."