Unlike some of its competitors, Johnson & Johnson’s vaccine does not need to be frozen and may require just one shot instead of two.
By Carl Zimmer
Buoyed by positive results in its earlier 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 so-called Phase 3 trials in the United States, Johnson & Johnson’s 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 subzero temperatures, and it may require just one dose instead of two.
“It would be fabulous if we had something at a single dose,” said Dr. Judith Feinberg, the vice chairwoman for research in medicine at West Virginia University, who was not involved in the study.
Only a Phase 3 trial, which compares the effects of a vaccine with those of a placebo, could determine if a single dose was indeed effective, Dr. Feinberg said. But if it worked, that could greatly speed efforts to curb the pandemic.
“The real issue here is time,” she said. “We’ve got to vaccinate a lot of people really quickly.”
The trial started on Monday. At a news conference on Tuesday, Dr. Paul Stoffels, chief scientific officer of Johnson & Johnson, said the company might be able to determine by the end of the year if the vaccine is safe and effective. The company will soon be posting a manuscript online with data from the earlier phases of its trials, he said.
Johnson & Johnson’s experimental vaccine uses an adenovirus to carry a gene from the coronavirus into human cells. The cell then produces coronavirus proteins, but not the coronavirus itself. These proteins can potentially prime the immune system to fight off a later infection by the virus.
Adenovirus vaccines must be kept refrigerated but not frozen, unlike the two front-runner vaccines, by Moderna and Pfizer, which depend on bits of genetic material known as mRNA. The freezing requirement could make the distribution of those vaccines difficult, especially to places without advanced medical facilities.
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