November 03, 2021
A real-world study found Johnson & Johnson's COVID-19 vaccine to be 73.6% effective, a figure similar to the efficacy rating observed during clinical trials.
But some vaccine experts say this research adds to a growing body of evidence suggesting there is room for improvement.
The study, published in JAMA Network Open, assessed nearly 100,000 patients within the Mayo Clinic Health System between February and July. About 1 in 40 unvaccinated patients tested positive for COVID-19, but only 1 in 148 vaccinated patients did. Researchers calculated that the vaccine led to a 3.73-fold reduction in infections.
The vaccine also reduced the risk of hospitalization and intensive care unit admission. Researchers did not have enough information to determine how well the J&J shot prevented COVID-19 deaths.
During clinical trials, the J&J vaccine was found to be 66.9% effective against moderate to severe COVID-19.
In a commentary accompanying the study's findings, Dr. Mohammad Sajadi and Zahra Rikhtegaran Tehrani, of the Institute of Human Virology at the University of Maryland School, argued that it is becoming more clear that the efficacy of the J&J vaccine's single-dose regimen is "inferior" to the two-dose Moderna and Pfizer-BioNTech vaccines.
They noted that another study found the real-world effectiveness of the Pfizer vaccine was 86.1% and the Moderna vaccine was 93.3%.
The J&J vaccine's efficacy can be improved with a second J&J dose or a booster of the Pfizer or Moderna vaccines, they noted. The U.S. Food and Drug Administration has authorized these options for anyone who received the J&J vaccine.
A recent National Institutes of Health study found that a second J&J shot quadrupled a person's antibody response. But a Pfizer booster led to a 35-fold increase and a Moderna booster prompted a 76-fold increase.
In a head-to-head study of all three vaccines, released in September, Moderna's vaccine was slightly more effective at preventing hospitalization than Pfizer's. It provided 93% protection while Pfizer's effectiveness rate was 88%. The J&J vaccine was 71% effective.
Moderna has hit a snag in getting its vaccine authorized for children. The FDA has pushed back its decision to authorize the vaccine for children ages 12-17 while its scientists investigate reports of myocarditis after vaccination.
An increased risk of myocarditis – inflammation of the heart muscle – has been linked to both the Pfizer and Moderna vaccines. The potentially serious side effect has occurred most often in adolescent males and young adults, and after the second dose.
Still, the U.S. Centers for Disease Control and Prevention and the World Health Organization have said the likelihood of myocarditis after vaccination is rare and cases are generally mild.
Because of this delay, Moderna also plans to wait to file for emergency use authorization for its vaccine for children ages 6-11. Last month, it released interim data suggesting the vaccine is safe for this population, too.
The authorization process for Pfizer has gone much faster. On Monday, the CDC endorsed the vaccine for children as young as 5 years old. The recommendation came after the CDC's Advisory Committee on Immunization Practices voted unanimously in favor of recommending the shots for younger children.
No cases of myocarditis after the vaccine were reported in the clinical trial on children 5-11. The most common side effects were fever or redness at injection site and they were mostly mild to moderate.