Around the world, more than 100 candidate vaccines against SARS-CoV-2 are in various stages of development and testing. On May 18, US biotech firm Moderna revealed the first data from a human trial: its COVID-19 vaccine triggered an immune response in people, and protected mice from lung infections with the coronavirus SARS-CoV-2. The current study was an open-label Phase I trial on 45 healthy adults. The participants received two doses four weeks apart of Moderna’s messenger RNA vaccine (mRNA-1273) at doses of 25 μg, 100 μg, or 250 μg. There was no comparison group, and, a significant limitation, the researchers did not screen the participants for SARS-CoV-2 infection by serology or polymerase chain reaction before enrollment. The study protocol calls for assessments at multiple points after each vaccination: 7, 14, 57, 119, 209, and 394 days. On days 1, 15, 29, 36, 43, and 57, the researchers tested each participant for binding antibodies and for neutralizing activity. Three of the 45 participants did not receive the second dose, one of whom developed urticaria and one who was in isolation for suspected COVID. On day 57, the researchers were able to detect binding and neutralizing antibodies with all three doses by 14 days after immunization with a peak at 28 days. The high-dose vaccine induced the greatest immunogenic responses but also the highest rate of adverse effects. Additionally, as we have observed with the new recombinant zoster vaccine, the second dose triggers more frequent adverse events: 54%, 100%, and 100% for each of the three doses, respectively. Fortunately, most of these were considered to be mild, and only three participants receiving the highest dose reported one or more serious adverse effects (21%). The adverse events included fever, arthralgias, injection site pain, headache, and chills. These are early and incomplete data from a small study with no control group, but the data provide hope that an effective vaccination is feasible.The mRNA-1273 vaccine induced anti–SARS-CoV-2 immune responses in all participants, and no trial-limiting safety concerns were identified.

Written by Henry C. Barry, MD, MS, on July 15, 2020. (Source: Jackson LA, Anderson EJ, Rouphael NG, et al. An mRNA vaccine against SARS-CoV-2—preliminary report [published online July 14, 2020]. N Engl J Med. 2020.

  1. Oxford-Astra-Zeneca Study :
  2. Pfizer-BioNTech Study:
  3. Regeneron Study:
  4. CanSino Biologics Study :