NEW YORK (BLOOMBERG) - Johnson & Johnson's experimental one-shot Covid-19 vaccine generated a long-lasting immune response in an early safety study, providing a glimpse at how it will perform in the real world as the company inches closer to approaching United States regulators for clearance.
More than 90 per cent of participants made immune proteins, called neutralising antibodies, within 29 days after receiving the shot, according to the report, and all participants formed the antibodies within 57 days.
The immune response lasted for the full 71 days of the trial.
"Looking at the antibodies, there should be good hope and good reason that the vaccine will work (in the company's late-stage clinical trial that's soon to report results)," Johnson & Johnson chief scientific officer Paul Stoffels said on Tuesday in an interview.
The one-shot vaccine generates more neutralising antibodies than a single dose of other front-runner Covid-19 vaccine, all of which are two-shot regimens. But when compared with two shots of these rivals, the response to Johnson & Johnson's single shot is in the same range, Dr Stoffels said.
Interim results from the phase 1/2 trial of 805 participants aged 18 and above were published on Wednesday (Jan 13) in the New England Journal of Medicine. The data expanded on more limited findings that Johnson & Johnson first published in September.
Johnson & Johnson's progress is being closely watched by top infectious disease experts because its vaccine has the potential to become the first that can protect people after just one shot, making mass-vaccination campaigns much easier. The company expects to get definitive efficacy data from a final-stage study by early next month, potentially leading to regulatory authorisation by March.
The US has granted emergency-use authorisations to two vaccines, one developed by Pfizer-BioNTech and the other by Moderna. Both employ a technology called messenger RNA that has never before been used in an approved product, and each showed more than 90 per cent efficacy against Covid-19 symptoms.
Those results were better than expected. US government officials had earlier said any vaccine with greater than 50 per cent efficacy would be considered a success. Based on that guidance, Johnson & Johnson aimed for 60 per cent effectiveness, Dr Stoffels said, but "we hoped and we planned for 70 per cent".
Within weeks, Johnson & Johnson will learn how its vaccine performed in a late-stage trial of 45,000 volunteers. Dr Stoffels now thinks it has the potential to be even higher than 70 per cent effective, based on the early-stage findings and other factors.
When the antibody response to Johnson & Johnson's shot is compared to others that have been through final stage trials, "there's a good reason to believe we can get into very high levels of efficacy", Dr Stoffels said. "Will it be north of 90 per cent? I don't know. The data will tell us."
Dr Moncef Slaoui, the chief scientific adviser to the US Operation Warp Speed vaccine development and distribution effort, said on Wednesday that he anticipates Johnson & Johnson's one-shot vaccine will show 80-85 per cent effectiveness against Covid-19. Johnson & Johnson and its government partners cannot see the data for the time being, a standard measure to prevent bias.
Experts have said that a single-shot vaccine offers advantages: ease of distribution and administration. Vaccines from Moderna, AstraZeneca-Oxford, and Pfizer-BioNTech all require two shots, which means repeat shipping and clinic visits. While Moderna and Pfizer-BioNTech's shots must be frozen, Johnson & Johnson's shot can be stored at refrigerator temperatures for three months.
"A single dose is going to be so much more effective in the world," Dr Stoffels said. "We are very confident that it works."
He added that another trial which Johnson & Johnson is conducting of its vaccine plus a booster shot "will give us a backup".
The study released on Wednesday also found that a second dose of Johnson & Johnson's shot, administered two months later, led to a three-fold increase in neutralising antibodies. Dr Stoffels said that is positive news, as the drugmaker is still evaluating how long immunity from the single-shot will last, and whether higher antibody levels will be needed to combat new strains of the virus.
Johnson & Johnson kicked off the separate late-stage study of its two-dose vaccine regimen in November. Dr Stoffels said the company is likely to finish enrolling the 30,000 participants before the end of first quarter, likely in March or April, and expects a data readout come summer.
Johnson & Johnson's vaccine candidate is made from a cold virus, called an adenovirus, that is modified to make copies of the coronavirus' spike protein, which the pathogen uses to enter cells.
Though the altered virus cannot replicate in humans, it induces an immune response that prepares the body for an actual Covid-19 infection. It was first developed with researchers at Harvard University who have spent years working on the adenovirus platform, which is also used in Johnson & Johnson's Ebola vaccine, as well as its Zika, RSV, and HIV investigational vaccine candidates.
The New England Journal of Medicine report showed that the vaccine was well-tolerated across the study participants. There was no difference in the immune response in younger participants and the elderly, which is important given older populations are most vulnerable to the disease.
The most frequent side effects were fever, fatigue, headache, muscle pain and injection-site pain.