2nd Dose of Johnson & Johnson COVID-19 Vaccine Gives Stronger Protection, Company Says

By Zachary Stieber
Zachary Stieber
Zachary Stieber
Zachary Stieber covers U.S. news and stories relating to the COVID-19 pandemic. He is based in Maryland.
September 21, 2021 Updated: September 21, 2021

A booster dose of Johnson & Johnson’s COVID-19 vaccine gives elevated protection against the virus that causes COVID-19, the company said Tuesday.

Johnson & Johnson said data from a Phase 3 clinical trial its researchers are helping run showed that a second shot of its vaccine provides 75 percent protection against symptomatic COVID-19 globally, and 94 percent effective against symptomatic COVID-19 in the United States.

The booster, when given two months after the first shot, caused antibody levels in recipients to rise four to six times higher than the levels observed after the single shot, the company said.

The trial also tested giving the booster six months after the initial jab. In those cases, antibodies climbed nine-fold one week after the booster and kept climbing, to 12-fold higher, a month after the booster.

The findings come from a trial dubbed ENSEMBLE 2 that is run by researchers with Janssen, a Johnson & Johnson subsidiary, and other researchers across the United States and additional countries.

The full dataset was not released. Johnson & Johnson said it plans to submit the data for publication in a peer-reviewed journal in the coming months.

The company also pointed to a preprint study conducted by its researchers in conjunction with Harvard University that found the jab was 79 percent effective against COVID-19 related infections and 81 percent effective for COVID-19 related hospitalizations.

“Our single-shot vaccine generates strong immune responses and long-lasting immune memory. And, when a booster of the Johnson & Johnson COVID-19 vaccine is given, the strength of protection against COVID-19 further increases,” Dr. Mathai Mammen, global head of R&D for Janssen, said in a statement.

Outside scientists shared the findings, but highlighted the wide-ranging confidence intervals. For instance, the confidence interval for the effectiveness of the booster in the United States against symptomatic disease was 58 percent to 100 percent.

“While the confidence intervals are huge, there’s evidence that boosting with a 2nd shot (of J&J) increases effectiveness,” Dr. Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan, wrote on Twitter.

“We need to see the full dataset but hopefully when it’s examined in detail, it will support a recommendation for those who got J&J to get a second shot. All the data (for any COVID vaccine) suggests there’s substantial benefit to boosting,” she added.

Johnson & Johnson’s jab is one of just three authorized or approved for use in the United States. It is far less commonly used than the shots from Moderna and Pfizer and is less effective, according to multiple previous studies.

U.S. regulators have held back authorizing boosters for Johnson & Johnson’s vaccine. They’re currently considering authorizing boosters for Pfizer’s vaccine after a Food and Drug Administration panel last week voted down a recommendation for boosters for everybody, opting instead to advise the agency to give the greenlight for boosters for those 65 and older.

Zachary Stieber
Zachary Stieber covers U.S. news and stories relating to the COVID-19 pandemic. He is based in Maryland.