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Experimental coronavirus vaccine highly effective

Results from a clinical trial showed that a COVID-19 vaccine developed by NIH and the biotech company Moderna is safe and effective. FG Trade / E+ via Getty Images

Researchers have been working to develop a safe and effective vaccine against SARS-CoV-2, the coronavirus that causes COVID-19. One vaccine candidate, called mRNA-1273, is being developed by researchers at NIH’s National Institute of Allergy and Infectious Diseases (NIAID) and the biotech company Moderna, Inc. Early results showed it can trigger an immune response against the virus without serious side effects.

To further investigate the safety and efficacy of this vaccine, a research team led by Dr. Lindsey R. Baden of Brigham and Women’s Hospital in Boston, Dr. Hana M. El-Sahly of Baylor College of Medicine, and Dr. Brandon Essink of Meridian Clinical Research carried out a clinical trial with more than 30,000 adult volunteers nationwide. Participants were 18 years of age or older with no known previous SARS-CoV-2 infection. Results were published on December 30, 2020 in the New England Journal of Medicine.

Volunteers were randomly assigned to receive either two doses of the investigational vaccine (100 micrograms each) or two shots of a saline placebo. They received the first injection between July 27 and October 23, 2020. The second shot was given 28 days after.

The investigators recorded 196 cases of symptomatic COVID-19 among participants at least 14 days after they received their second shot. Only 11 of these cases were in the group that received the vaccine, with none severe. In contrast, 185 of the cases occurred in the placebo group, 30 of which were severe. The incidence of symptomatic COVID-19 was thus 94.1% lower in participants who received mRNA-1273 compared to those receiving placebo. For participants 65 years or older, the efficacy was 86.4%.

There were no concerning safety issues with vaccination. Local reactions to the vaccine were generally mild. About half the participants receiving mRNA-1273 experienced moderate to severe side effects—such as fatigue, muscle aches, joint pain and headache—after the second dose. In most volunteers, these resolved within two days.

One potential concern about COVID-19 vaccines is an unusual phenomenon called vaccine-associated enhanced respiratory disease, or VAERD. VAERD can occur when a vaccine induces an immune response that causes the disease the vaccine is supposed to protect against to be more severe if you’re exposed to the virus. However, the team found no evidence of VAERD among those who received mRNA-1273.

“There is much we still do not know about SARS-CoV-2 and COVID-19. However, we do know that this vaccine is safe and can prevent symptomatic COVID-19 and severe disease,” says NIAID Director Dr. Anthony S. Fauci. “It is my hope that all Americans will protect themselves by getting vaccinated when the vaccine becomes available to them. That is how our country will begin to heal and move forward.”

The FDA issued an for Moderna to make the vaccine available for the prevention of COVID-19 in adults on December 18, 2020.

Although mRNA-1273 can prevent symptomatic COVID-19, more study is needed to determine whether it protects against SARS-CoV-2 transmission. Additional analyses are also underway to understand the vaccine’s impact on asymptomatic infections.