- Researchers running an early clinical trial of an experimental coronavirus vaccine developed by Johnson & Johnson on Friday disclosed the first data from their study, just two days after the drugmaker launched a large-scale test of the shot in the U.S. and seven other countries.
- Results, which were published online as a draft manuscript, are preliminary and don't prove whether or not the vaccine can protect against coronavirus infection or COVID-19. But the findings are supportive of further study, showing vaccination led to immune responses in nearly all trial volunteers after a single injection.
- Since the trial is still ongoing, with some participants still to receive an exploratory second shot, the researchers disclosed pooled safety results for both the vaccine and placebo groups together, making it more difficult to determine how well tolerated vaccination was. Side effects were more common and more severe in younger participants.
Expectations are high that J&J can deliver a coronavirus shot that can accomplish in one dose what other developers's candidates need two to do.
The study results disclosed Friday suggest that goal is possible, and were strong enough to convince J&J to move forward with a single-injection regimen for its global Phase 3 trial that began on Wednesday.
Like other vaccine developers before it, J&J can now claim its vaccine appears to be working as intended, although the preliminary nature of Friday's data leaves several important questions unanswered.
Results are from a Phase 1/2 study J&J is conducting in the U.S. and Belgium, which tested several different vaccine doses and regimens against placebo in about 800 healthy adults. Researchers are still collecting data, and participants haven't yet received their second vaccination, which occurs 57 days after their first.
But the interim analysis shows that, four weeks after vaccination with J&J's shot, participants' immune systems were generating antibodies that could bind to and neutralize SAR-COV-2.
Since the virus is still so new, scientists don't yet know how many of these antibodies are needed to protect someone from infection or disease. Rather than guess, researchers have compared antibody levels brought on by inoculation to the number found in the blood of recovered COVID-19 patients, samples called convalescent sera.
On that measure, J&J's vaccine led to antibody levels that were in a similar range, but noticeably lower, than those for the comparator panel of convalescent sera they used.
J&J researchers noted, however, that results for several participants may be artificially lower because of their test's measurement limits. If re-analyzed using a wider range of measurement, the average antibody levels might climb higher.
Early data from Moderna, Pfizer, AstraZeneca and Novavax showed their respective shots triggered neutralizing immune responses that were, to varying degrees, either at or above convalescent sera levels. Comparing across trials, and across vaccines, is challenging, however. Developers use their own panels of convalescent sera as comparisons, and have different tests to assess antibody responses.
More importantly, Phase 1 studies are designed to assess the safety of an experimental vaccine before it's given to wider groups of people.
J&J's data are harder to assess, though, because researchers remain "blinded" to whether participants received the vaccine or the placebo. Instead, they presented in the manuscript pooled data for both groups together.
Most participants reported generally mild side effects like injection site pain, tiredness, headache and, in 20% of the volunteers aged 18 to 55, fever. Twenty-two, or 5%, of the participants had higher fevers rated more severe.
Reactions were fewer in the group of adults aged 65 or older. Only 4% reported fever, and none had elevated temperatures that were classified as Grade 3, or restrictive of daily living activities.
"This finding suggests that the vaccine candidate is less reactogenic in older adults," the researchers wrote, which could be potentially important as the elderly are considered to be at higher risk for COVID-19 and are likely to be vaccinated before younger, healthy adults.
Across all groups, 12 individuals reported a range of other side effects that were also classified as Grade 3, including one person who was hospitalized overnight with a fever.
J&J's shot is what's known as a viral vector vaccine, constructed from an uninfectious adenovirus, or cold virus, that's modified to carry the genetic instructions for SARS-CoV-2's characteristic spike protein. AstraZeneca and the University of Oxford are using the same technology for their vaccine, but have chosen to use an adenovirus found in chimpanzees.
While the approach is newer than more established vaccine-building techniques, J&J uses the same technology for its Ebola vaccine, which was recently approved in Europe.
Should testing prove J&J's vaccine to be safe and effective against SARS-CoV-2, the drugmaker expects it could have the first batches available for potential use by early 2021, and enough production capacity to make 1 billion doses a year.