In-Depth on the Johnson & Johnson vaccine’s safety and effectiveness

Single dose is 85% effective against severe COVID

By: Derek Staahl

SAN DIEGO (KGTV) — Johnson and Johnson says its single-dose vaccine provides strong protection against severe cases of COVID-19, but it is somewhat less effective overall than the two mRNA vaccines currently in use.

The company released topline results Friday from its Phase 3 trial involving nearly 44,000 volunteers. The overall effectiveness was 66 percent in preventing moderate to severe cases of the virus and 85 percent effective in preventing the most severe cases of COVID-19.

Twenty-eight days after the shot, none of the vaccinated volunteers had to be hospitalized.

“I would give it like a B+ overall,” said UC San Francisco infectious disease expert Dr. Peter Chin-Hong.

“The fact that if you get this vaccine, even if you get COVID, it’s milder COVID and you don’t go to the hospital, that’s pretty good,” he said. “Remember the flu vaccine is only 40 to 60 percent effective. If it prevents me from going to the hospital, I’m all for it.”

The data suggests Johnson and Johnson’s vaccine fortifies the immune system over time, with some protection detected at 14 days and full protection at 28 days. By day 49, no vaccinated volunteer got a severe case of the disease.

However, the vaccine’s potency varied significantly by region, suggesting it may be susceptible to viral mutants.

The trial was conducted in eight countries grouped into three regions. In the U.S., it was 72 percent effective at preventing disease. But in South Africa, where an elusive variant of the virus is common, the vaccine was just 52 percent effective.

Johnson and Johnson said it is already working on an update to its vaccine that could be deployed in countries where the South Africa variant is common.

“We didn’t quite hit the 95 percent efficacy of the two other mRNA vaccines, but there are certainly some advantages” to the Johnson and Johnson vaccine, said Dr. Christian Ramers, an infectious disease specialist at Family Health Centers of San Diego who serves on San Diego County’s vaccine advisory board.

“First of all the volume to get more vaccine. The storage is going to be easier, and then the fact that this is a single dose really helps us a lot,” he said.

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