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

Single dose is 85% effective against severe COVID
johnson & johnson vaccine medical
Posted at 4:46 PM, Jan 29, 2021
and last updated 2021-01-29 20:48:29-05

SAN DIEGO (KGTV) -- Johnson and Johnson says its single-shot 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.”

RELATED: How the Moderna and Pfizer vaccines stack up in terms of safety, efficacy

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.

The company says its viral vector vaccine can be stored in a normal refrigerator for at least three months. Pfizer and Moderna's mRNA vaccines have to be kept frozen, necessitating a cold chain of distribution that poses an immense challenge in developing countries.

Detailed safety data about the side effects of the Johnson and Johnson vaccine won’t be released until the company submits an application to the FDA, but an independent safety board reported no significant safety concerns.

The viral vector vaccine uses a delivery method called AdVac that has been previously approved in a vaccine against Ebola and used in investigational vaccines for HIV and Zika. “The safety profile was consistent with other vaccine candidates using Janssen’s AdVac technology among more than 200,000 people to date,” the company said.

The company said 9 percent of volunteers developed a fever shortly after the injection. That is lower than the 14.8 percent reported in the Moderna trial and the 14.2 percent in the Pfizer trial.

Johnson and Johnson said there were no cases of severe allergic reactions or anaphylactic shock that have popped up during the rollout of the Pfizer and Moderna vaccines. However, there were no cases of anaphylaxis detected in those trials either; the rare cases began emerging once the vaccines hit the market.

A December report from the CDC showed the rate of anaphylaxis was about one in 90,000 for the Pfizer vaccine. About one in 400,000 people experienced anaphylaxis after Moderna’s vaccine, or 2.5 cases per one million doses. Some experts suspect a compound in the fatty bubble used to transport the mRNA might cause the reactions, particularly one called polyethylene glycol or PEG.

Dr. Ramers said we will have to wait to see if the Johnson and Johnson vaccine triggers any cases, but it does not contain the fatty lipid bubble.