After a single injection of the vaccine, they waited six weeks and then infected the animals with the coronavirus. Six of the seven vaccine variants offered monkeys partial protection against the coronavirus, meaning that the virus replicated only at low levels in the animals.
The seventh version proved more powerful than the rest: Five out of six monkeys that received it had no detectable viruses at all. The sixth had only low levels in its nose.
“The fact that we could protect with a single shot in animal models was quite a positive surprise to us,” said Dr. Paul Stoffels, the chief scientific officer of Johnson & Johnson.
It was this best-performing vaccine that Johnson & Johnson used last week to begin its first human safety trial, a so-called Phase 1 trial. If it goes well, the company hopes by September to enter Phase 3 trials, which test not only whether the vaccine is safe, but also whether it works.
The company plans on testing both single and double doses. Dr. Rasmussen said that a vaccine that proved effective with a single dose would make it far easier to treat the billions of people who need it. “Theoretically, you would need less of it, so you give it to more people more quickly,” she said.
Inovio, a company developing a DNA-based vaccine, announced Thursday that monkeys challenged four months after vaccination had a reduced load of the virus in their nose and lungs. Their report has not yet been published in a scientific journal.
AstraZeneca and the University of Oxford have developed a vaccine based on yet another type of modified virus, called ChAdOx1. In May, they released promising monkey data, which was also published on Thursday in Nature. The team is now running Phase 3 trials in people, which could produce results by October.
“It’s exciting to see the number of platforms that are showing promise for a vaccine,” said Stacey L. Schultz-Cherry, a virologist at St. Jude Children’s Research Hospital in Memphis who was not involved in any of the trials.