Moderna coronavirus vaccine shows 'acceptable safety' and immune response in older adults

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(CNN) - A COVID-19 vaccine developed by the biotechnology company Moderna in partnership with the National Institutes of Health has been tested in older adults and found to safely elicit an immune response in that age group, according to preliminary data.

"The immune response to many other vaccines has been shown to decrease with increasing age. Thus, the testing of SARS-CoV-2 vaccine candidates in older populations is of paramount importance, since these persons account for the majority of serious COVID-19 cases and associated deaths," the NIH-led researchers wrote in the study, published in the New England Journal of Medicine on Tuesday. SARS-CoV-2 is the name of the coronavirus that causes COVID-19.

Moderna expanded a Phase 1 clinical trial of its vaccine, called mRNA-1273, to include 40 participants ages 56 and older. The participants enrolled in the trial between April 16 and May 12. They were given two doses of either 25 micrograms or 100 micrograms of vaccine, 28 days apart.

The trial — conducted at sites in Seattle, Atlanta and Bethesda, Maryland — found that adverse events from the vaccine were mostly mild or moderate and included fatigue, chills, headache, muscle pain and pain at the injection site. Those events were more common after the second dose of vaccine, according to the study.

One participant developed a nail infection and rash, and another had hypoglycemia or low blood sugar — but the researchers noted that those were considered not related to vaccination.

Overall, the preliminary findings showed that a two-dose vaccine series in older adults had "an acceptable safety" profile and the 100 microgram dose induced a greater immune response than the 25 microgram dose, which the researchers noted supports the idea to continue testing the vaccine at the 100-microgram dose level and as a two-dose regimen in a Phase 3 trial.

The researchers also noted that they did not observe "systematic differences" between the older adults in this study and the younger adults, ages 18 to 55, in their original trial. But it’s not clear if the antibody responses seen in the volunteers indicate they are protected from infection, the researchers said.

More research is needed to determine whether similar findings would emerge among a larger and more diverse group of participants. Moderna is testing its vaccine in an advanced, Phase 3 trial that’s expected to include 30,000 volunteers.

This story was first published on CNN.com, "Moderna coronavirus vaccine shows "acceptable safety" and immune response in older adults"