A photo of the Massachusetts-based Moderna’s headquarters in Cambridge.
A photo of the Massachusetts-based Moderna’s headquarters in Cambridge.
Photo: Getty Images

An experimental vaccine for covid-19 is showing some promising (though still very preliminary) results in people, according to its manufacturer. On Monday, biotech company Moderna announced its incomplete findings from a Phase 1 clinical trial of the vaccine candidate, called mRNA-1273. The trial found that the vaccine was overall tolerable and safe, and many of the participants also appeared to create antibodies to SARS-CoV-2, the coronavirus that causes covid-19.

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The trial, funded partly by the U.S. National Institutes of Health, involved 45 healthy male and female volunteers between the ages of 18 and 55. They received one of three doses administered via arm injection twice over a 28-day span—either a 25, 100, or 250 milligram dose per injection. Their blood was then routinely measured for antibodies.

Phase 1 clinical trials are expressly designed to test for the safety of an experimental treatment, with any considerations about its effectiveness being secondary. By that standard, the vaccine seemed to pass. According to the company, three people who took the highest dose of the vaccine experienced a grade 3 adverse event after the second dose, while one person in the 100-milligram group experienced grade 3 redness around the injection site. No one in the 25-milligram group experienced any similar events. Grade 3 refers to reactions that are considered severe but not life-threatening. All reported adverse events were short-lasting and went away on their own, the company said in its announcement.

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At this point, Moderna said that it has data available from the low- and medium-dose groups when it comes to antibody levels. In the 25-milligram group, two weeks after the second dose, all of the volunteers appeared to show levels of binding antibodies similar to those seen in plasma donated from recovered covid-19 patients. The 100-milligram group had higher average levels of these antibodies than the levels in plasma donors.

Binding antibodies are important for the immune response to any particular germ, but they don’t actually prevent infection on their own. Neutralizing antibodies, however, can stop viruses from infecting other cells. Of the eight participants with data available, the company said, all of them seemed to produce levels of neutralizing antibodies at levels similar to or higher than recovered covid-19 patients.

The company also announced successful results from a mouse study. Mice given the vaccine appeared to fend off the virus from growing in their lungs, the study concluded. The levels of neutralizing antibodies measured in the mice with no infection correlated with the levels found in the human volunteers.

These two studies combined, said Tal Zaks, chief medical officer at Moderna, “substantiate our belief that mRNA-1273 has the potential to prevent COVID-19 disease and advance our ability to select a dose for pivotal trials.

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Of course, these are very early results. While this is the first research released from a human trial of a potential covid-19 vaccine, Moderna’s data has yet to be independently verified and isn’t complete. Even if it was, promising results from Phase 1 trials often don’t translate to effective, approved treatments down the line. But for now, there’s reason to be optimistic.

According to the company, preparations are now underway for larger, Phase 2 trials of the vaccine, which will involve people taking a 50- or 100-milligram dose. Should things continue to go well, Moderna also expects to start recruiting people for a Phase 3 trial later this July, pending government approval.

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At least 110 vaccine candidates are being studied right now, according to the World Health Organization, with eight in human trials as of May 15. Experts generally still believe that any successful vaccine will take upwards of a year if not longer to be widely available to the public.

Science writer at Gizmodo and pug aficionado elsewhere

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