A COVID-19 vaccine shows positive but somewhat disappointing results in the first stage of testing, according to a new study published Friday in The Lancet medical journal.
The vaccine tested in China triggered an immune response in most, but not all, patients, and many had negative side effects.
The study is the first to publish results from the initial phase of testing of a COVID-19 vaccine. More than 100 others are in development around the world, including nine others in clinical trials.
"If it was the only vaccine available, I think many people would take it," said Gary Simon, head of the infectious disease division at George Washington School of Medicine and Health Sciences in Washington, D.C.
However, he added, "unless they can make it more tolerable, I can't see how it's going to be a major player."
The small, preliminary trial tested 108 healthy volunteers in Wuhan, China, where the coronavirus first surfaced. The vaccine was developed by China-based CanSino Biologics with backing from the Chinese government.
After 28 days, half of those given low- or middle-dose levels of the vaccine produced neutralizing antibodies, the kind that would block infection. Three-quarters of those given the largest dose did.
Nearly all patients developed a positive response from a separate part of the immune system, within 14 days.
It's not known yet whether either of these responses will be enough to protect patients. This early phase of testing is not designed to determine whether the vaccine works. It only tests whether the vaccine is safe and whether the immune system responds to it.
There were safety problems. The shot gave more than half the recipients sore arms. Nearly half developed a fever, including one serious case. About 40 percent had headaches or fatigue.
"Given that there was a safety issue, given that many patients didn't have high [levels of] neutralizing antibodies, I would say this is a singularly unimpressive study," said Paul Offit, director of the vaccine education center at Children's Hospital of Philadelphia.
"I have no doubt there are going to be a number of vaccines that emerge that are going to be both safer and better than this vaccine appears to be," Offit added.
The study covers only the first 28 days after injection. Final results will be evaluated in six months.
The vaccine is moving into a larger trial in Wuhan.
Leader of the pack
The report is the latest in a series of recent vaccine research announcements offering some tentative encouraging news.
Biotech company Moderna says its vaccine produced neutralizing antibodies in all eight patients for which it has results.
The company has not released the data, however, and scientists have expressed concerns about transparency.
But the studies also found signs that even if these vaccines keep people from getting sick, the shots might not stop them from spreading the disease.
Vaccinated animals still had the virus in their noses and throats. If the same thing happens in humans, and if those viruses can infect other people (both of which are far from certain at this point), then "to protect the population we're going to have to be vaccinating many, many more people," said Sarah Fortune, head of the infectious diseases department at Harvard T.H. Chan School of Public Health.
"I think it's a little bit sobering to see that while we may get protection against disease," she said, "we may not get nearly as effective protection against transmission."
Offit said there is no way of knowing whether any of these vaccines is truly safe and effective until it's been tested on tens of thousands of people.
"I think we should really wait and try not to predict what's going to happen until we see the proof in the pudding," he said.
With more than 335,000 dead and economies devastated worldwide, companies and governments are racing to produce a vaccine as soon as possible. Some are taking the unusual (and potentially costly) step of ramping up manufacturing of several vaccines before the proof is in.
Moderna has signed a deal to begin manufacturing its vaccine in July, with backing from the U.S. government.
The Trump administration announced that by October it would have at least 300 million doses of the Oxford vaccine available, through an agreement with pharmaceutical company AstraZeneca.
That timeline worries Offit.
"I can't imagine that we would have the kinds of data we need to make sure that these vaccines are safe and effective," he said.
"I just worry that there is a political drive to this, that they just want to make sure that we have something before the election" in November, he said.
"What we need are the data," Offit added. "I hope this isn't politicized."