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Encouraged by the positive results of its previous studies, Johnson & Johnson has begun the final stage of clinical trials for its coronavirus vaccine.
Although they are a couple of months behind the other Phase 3 trials in the United States, the Johnson & Johnson trials will be the largest, with plans to enroll 60,000 participants. And the experimental vaccine may have considerable advantages over some of its competitors, experts said. It does not need to be stored in freezing temperatures and may require just one dose instead of two.
“It would be great if we had something in just one dose,” said Dr. Judith Feinberg, vice president for research in medicine at West Virginia University, who was not involved in the study.
Only a phase 3 trial, comparing the effects of a vaccine to those of a placebo, could determine whether a single dose was really effective, Dr. Feinberg said. But if it works, that could greatly accelerate efforts to curb the pandemic.
“The real problem here is time,” he said. “We have to vaccinate a lot of people very quickly.”
The trial began on Monday. At a news conference Tuesday, Dr. Paul Stoffels, Johnson & Johnson’s chief scientific officer, said the company could determine by the end of the year whether the vaccine is safe and effective. The company will soon publish a manuscript online with data from earlier phases of its trials, he said.
Johnson & Johnson’s experimental vaccine uses an adenovirus to carry a coronavirus gene into human cells. The cell then produces coronavirus proteins, but not the coronavirus itself. These proteins can potentially prepare the immune system to fight a subsequent virus infection.
Adenovirus vaccines must be kept refrigerated but not frozen, unlike the two pioneering vaccines from Moderna and Pfizer, which rely on fragments of genetic material known as mRNA. The freezing requirement could make it difficult to distribute those vaccines, especially in places without advanced medical facilities.
The Moderna and Pfizer vaccines also require two injections a few weeks apart, a major logistical hurdle.
“I mean, just think to yourself, how much easier would it be for you to go to your local doctor or your local pharmacy and be ready?” said Dr. Daniel Barouch, a virologist at Beth Israel Deaconess Medical Center.
Dr. Barouch led the development of the adenovirus vaccine in the early 2000s. Johnson & Johnson acquired it and used it to make vaccines for Ebola, HIV, respiratory syncytial virus, and Zika.
In all, 100,000 people have received the adenovirus vaccine in clinical trials for these four diseases, with no serious side effects.
Johnson & Johnson’s Ebola vaccine was licensed in Europe in June. In contrast, the designs of the other three coronavirus vaccines in phase 3 trials in the United States have not yet been licensed to treat any disease. (A different type of adenovirus is being used in AstraZeneca’s coronavirus vaccine trials, which have been stopped in the United States for safety reasons.)
Accustomed to the typically slow pace of vaccine research, Dr. Barouch has been in awe of the past eight months of rapid work on the coronavirus vaccine.
“It’s quite surprising,” he said in an interview. “We never would have thought it could be done so quickly.”
Dr. Barouch and his colleagues conducted a series of animal experiments to learn how the vaccine stimulates the immune system to fight the virus. In a critical experiment, the results of which were published in July, they found that the vaccine gave the monkeys enough antibodies to protect them from infection with the coronavirus.
Following these promising results in animals, Johnson & Johnson began small safety studies in people, known as phase 1/2 trials. Dr. Stoffel said that an analysis of 395 of the volunteers found no serious side effects. And they produced encouraging levels of antibodies even after a single injection, he said.
“The single dose could be enough to protect people for a long time,” he said.
A phase 1/2 trial measures immune responses, but cannot determine whether a vaccine actually protects against a virus. Dr. Barouch noticed that a single dose of the vaccine produced a level of antibodies in people that his previous experiments showed was sufficient to protect the monkeys.
The company plans to recruit up to 60,000 people over the age of 18 for its phase 3 trial in the United States, Argentina, Brazil, Chile, Colombia, Mexico, Peru and South Africa.
The trial is roughly twice the number of others initiated so far in the United States. (Last week, Pfizer announced that it planned to increase its trial from 30,000 to 44,000 people.)
Dr Barouch said the larger size would provide a better idea of the safety of the vaccine and could also reduce the time it takes to determine if the vaccine is effective. “It will provide a faster reading,” he said.
At the press conference, Dr. Stoffels said that Johnson & Johnson would publicly share its protocol for the phase 3 trial on its website.
Johnson & Johnson will test the single dose in the 60,000-person trial and will also conduct a smaller trial with a double dose.
But Dr. Barouch cautioned that the results of phase 3 trials cannot be fixed to a fixed date. If the trial takes place where there are relatively few cases, it will take longer before enough people contract Covid-19, the disease caused by the coronavirus, to know that it works. “It depends on where the epidemic is going,” he said.
Johnson & Johnson is most likely not the latest vaccine maker to announce Phase 3 trials in the United States soon. Companies like Novavax and Sanofi are conducting their own clinical trials. Their vaccines are based on different designs, such as packing bits of viral proteins into microscopic scaffolds, which can turn out as good or better than major competitors.
“We need several vaccines to make them work,” said Dr. Barouch, “because there are seven billion people in the world and no vaccine supplier will be able to make them on that scale.”
