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An epidemiologist breaks down the numbers on Johnson & Johnson’s single-dose vaccine

An image of a women receiving a vaccine in her left arm. (Photo by UTHealth).
The Johnson & Johnson vaccine is 85% effective at preventing severe illness, and most importantly, it was 100% effective at preventing hospitalization and death among trial participants. (Photo by: UTHealth)

While the Johnson & Johnson single-dose COVID-19 vaccine that has now received emergency use authorization by the U.S. Food and Drug Administration has a lower efficacy rate compared to other previously approved vaccines, an expert with The University of Texas Health Science Center at Houston (UTHealth) explains why it is still a significant step toward ending the COVID-19 pandemic.

“You may be quick to compare Johnson & Johnson’s figures to those of previously authorized vaccines, such as Pfizer or Moderna, but a 66% percent efficacy rate of preventing symptomatic illness is worth celebrating,” said Katelyn Jetelina, PhD, an assistant professor at UTHealth School of Public Health in Dallas.

The Phase III clinical trial included over 43,000 participants (21,895 in the vaccine group and 21,888 in the placebo group) and its data revealed the vaccine had an efficacy rate of 66.9% two weeks after vaccination, and dropped down to 66.1% after 28 days.

The Johnson & Johnson vaccine is 85% effective at preventing severe illness, and most importantly, it was 100% effective at preventing hospitalization and death among trial participants.

“It’s easy to look at the numbers and assume this vaccine is less effective, but when the race to develop a COVID-19 vaccine began, scientists were hopeful for a 50% efficacy rate. We have managed to knock that out of the park at least three times now, so we epidemiologists are still very excited about the vaccines with a perceived ‘lower’ efficacy rate,” Jetelina said.

On top of requiring just one dose, one major difference about this vaccine is that it does not require complex cold-chain storage. This will allow for much easier distribution, especially to areas where super chilled storage is limited, such as rural communities.

However, even with the addition of a third vaccine, experts caution that it is still critical for people to maintain COVID-19 safety measures, even once they are fully vaccinated. The continued practice of the guidelines issued by the Centers for Disease Control and Prevention to prevent spread of COVID-19 include wearing masks, physical distancing, hand hygiene, and staying home when feeling unwell.

“The bottom line is this, if you’re eligible to receive any COVID-19 vaccine, it’s important that you take the first opportunity you can. All of the vaccines granted authorization in the U.S. are safe and effective and we are hopeful that vaccines will help stop this pandemic,” Jetelina said.

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