A fourth Covid-19 vaccine candidate has gone into the final stage of clinical trials in the U.S., with Johnson & Johnson announcing the start of its Phase 3 trial Wednesday.

The drugmaker follows Pfizer and Moderna, whose Phase 3 trials began in late July. AstraZeneca also started its Phase 3 vaccine trial this month, but it remains on pause in the U.S. after a participant in the U.K. was reported to have developed a spinal cord injury.

The Johnson & Johnson trial is not expected to yield preliminary results for at least two months.

President Donald Trump has repeatedly pressed for faster work on vaccine research — even suggesting that there could be some kind of approval before the Nov. 3 election. That timeline would be impossible, at least for Johnson & Johnson, whose interim results are not expected until late November at the earliest.

Johnson & Johnson’s vaccine candidate, which is being developed in partnership with Janssen Pharmaceuticals, differs in several ways from the others that have reached the final stage of trials.

Unlike Pfizer’s and Moderna‘s vaccines — which require two doses about a month apart — the Johnson & Johnson vaccine can be administered fully in one dose, avoiding the complicated coordination to require that people return in time for the second dose.

In addition, the Johnson & Johnson vaccine requires basic refrigeration for storage. Pfizer’s vaccine must be stored at minus 94 degrees Fahrenheit. (For comparison, that’s colder than the South Pole’s average winter temperature: minus 76 degrees.)

Moderna has aimed to enroll 30,000 participants, and Pfizer expects to sign up 44,000 in U.S. Phase 3 trials. Johnson & Johnson’s enrollment will be much larger, aiming for 60,000 people.

The larger study is “notable and commendable,” said Dr. Gregory Poland, an infectious diseases expert who directs the Mayo Clinic’s Vaccine Research Group in Rochester, Minnesota. He said a single dose of vaccine in a pandemic provides an opportunity to fully vaccinate more people more quickly.

The Johnson & Johnson vaccine was made using a technique used in previous vaccines, including the one the company developed for the Ebola virus. It combines genetic material from SARS-CoV-2 (the virus that causes Covid-19) with an adenovirus, which causes the common cold but has been genetically altered to be harmless in this case.

Using the genetic material from the coronavirus, the disarmed adenovirus is able to teach the immune system to generate antibodies to attack SARS-CoV-2’s spike protein, which is what allows the virus to enter human cells.

The accelerated efforts to find a safe and effective Covid-19 vaccine are part of Operation Warp Speed under the departments of Defense and Health and Human Services. The Johnson & Johnson vaccine trials are sponsored in part by the National Institute of Allergy and Infectious Diseases.

Source : NBC News

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