The Janssen vaccine for COVID-19: Interim Phase III results

As this issue of TreatmentUpdate went to press, the Janssen corporation released the interim data from its phase III clinical trial.

A total of 44,325 adults were enrolled in Latin America, South Africa and the U.S. Participants were given the vaccine (or placebo) described previously in this issue of TreatmentUpdate. The Janssen corporation is using a modified adenovirus called adenovirus 26 into which it has inserted the genetic information to instruct cells to make a protein used by SARS-CoV-2.

Overall, 28 days after vaccination, the vaccine was 66% effective at reducing the risk of developing moderate or severe forms of COVID-19.

No one who received the vaccine died from COVID-19, while five deaths occurred in the placebo group. The efficacy of the vaccine at preventing severe COVID-19 varied from one geographic location to another as follows:

  • U.S. – 72% efficacy
  • Latin America – 66% efficacy
  • South Africa – 57% efficacy

It is possible that the efficacy differed by geography because of the different variants of the virus that are predominant in different places.

Further details may emerge in the future as the full results from phase III are released.

—Sean R. Hosein


National Institutes of Health. Janssen Investigational COVID-19 vaccine: Interim analysis of phase 3 clinical data released. Press release. 29 January 2019.