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Johnson & Johnson's Covid-19 Vaccine Is 73.6% Effective, According To New Real-World Study

(CNN) -- Data from a real-world study assessing Johnson & Johnson's Covid-19 vaccine finds it is 73.6% effective, according to research published Tuesday in the journal JAMA Network Open.

The study evaluated patients within the Mayo Clinic Health System between February and July of this year. The researchers followed nearly 9,000 patients vaccinated with the J&J vaccine and nearly 89,000 patients who were unvaccinated. They looked specifically to see how many of them tested positive for Covid-19.

Among the 8,889 vaccinated patients, 60 had a positive PCR test. Among the 88,898 unvaccinated patients, 2,236 had a positive PCR test. The researchers concluded the vaccine was 73.6% effective and led to a 3.73-fold reduction in coronavirus infections. The finding is similar to clinical trial data that found the vaccine was 66.9% effective against moderate to severe Covid-19.

The new research showed a reduction in severe cases, especially hospitalizations, but too few people got Covid-19 among the vaccinated group to draw a strong conclusion as to how well the vaccine prevented deaths.

In an accompanying commentary, Dr. Mohammad Sajadi of the Institute of Human Virology at the University of Maryland School of Medicine, argued that the findings are part of a growing body of work that suggests "room for improvement" with the J&J vaccine.

"What is becoming more clear with time is that the single-dose regimen of the [Johnsons & Johnson Covid-19] vaccine seems to be inferior to the mRNA vaccines in terms of [vaccine effectiveness]," Sajadi wrote, comparing the J&J vaccine to a different type of Covid-19 vaccine that is made by Pfizer/BioNTech and Moderna.

Sajadi noted that the same group of researchers who conducted this latest J&J study had previously looked at vaccine effectiveness of the Pfizer and Moderna Covid-19 vaccines, which had "significantly higher" efficacy. In that study, the real-world effectivness of the Pfizer vaccine was 86.1%. For Moderna it was 93.3%.

In September, a head-to-head study of all three vaccines found the Moderna vaccine is slightly more effective than Pfizer's in real-life use in keeping people out of the hospital.

Moderna's vaccine provided 93% protection against hospitalization, and Pfizer's was 88% effective.

Sajadi said improvement of the J&J vaccine may come in a second dose or a booster of an mRNA Covid-19 vaccine.

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