“It exceeds all expectations,” said Dr. Kizzmekia S. Corbett, a viral immunologist and leader of a team that developed the vaccine at the infectious disease institute.
More than half of the participants had side effects, including fatigue, chills, headaches, muscle aches and pain at the injection site. Some had fever. One person who received the low dose developed hives and was withdrawn from the study. None of the side effects were considered serious.
Experts not involved with the study said the results were encouraging, but early. “Just because you have antibodies doesn’t mean you’re completely immune,” Dr. Rasmussen said.
It is possible, she said, that a vaccine might not totally prevent infection, but that it might make the illness less severe. “If it’s a choice between a bad cold and being on a ventilator, I’ll take the bad cold,” she said.
Dr. Paul Offit, an infectious disease expert at the University of Pennsylvania and Children’s Hospital of Philadelphia, said that the neutralizing antibodies and other immune responses were a good sign, but that it was not known yet whether they would actually protect people against the virus, or how long they would last. The side effects were a “small price to pay” for protection against a potentially severe disease, he said, though fever may be a cause for concern once the vaccine is given to large numbers of people.
“You always worry that fever, especially high fever, could lead to other things,” Dr. Offit said, adding that only a large controlled study can determine whether the vaccine is truly safe and effective.
Otherwise, “it’s reading the tea leaves,” he said. “You just don’t know anything until you do a Phase 3 trial.”