Moderna’s COVID-19 Vaccine Appears Safe in Mouse Study with Single Dose Offering Protection

Studies in mice of Moderna, Inc.’s (Cambridge, MA, USA) COVID-19 vaccine candidate indicate that it is unlikely to increase the risk of the disease becoming more severe and only a single dose could provide protection against the novel coronavirus.

Moderna is currently conducting human trials of its COVID-19 vaccine candidate and plans to initiate final-stage trials in July that will involve 30,000 volunteers. Previous studies conducted on a vaccine for SARS, which belongs to the same family as the new virus that causes COVID-19, have suggested that such vaccines could increase the severity of the disease after the vaccinated person becomes exposed to the pathogen at a later stage, particularly among individuals who are unable to generate a sufficiently strong immune response. This risk is viewed by scientists as a significant obstacle that needs to be overcome ahead of human trials of any COVID-19 vaccines.


According to preliminary data from animal studies released by the US National Institutes of Allergy and Infectious Disease (NIAID) and Moderna, the researchers gave mice one or two shots of various doses of Moderna’s vaccine, including doses that were too weak to generate a protective immune response. After exposing the mice to the coronavirus, the researchers concluded that “sub-protective” immune responses do not result in vaccine-associated enhanced respiratory disease, a susceptibility to more severe disease in the lungs. Upon further testing, the researchers found that the vaccine induced antibody responses to block the virus from infecting cells.

According to the researchers, the vaccine also appeared to protect the lungs and noses against infection by the coronavirus without indication of any toxic effects. The team of researchers have noted that the mice which were given only a single dose of the vaccine before exposing them to the coronavirus after seven weeks were “completely protected against lung viral replication,” indicating that a single vaccination prevented the virus from replicating in the lungs.

Related Links:
Moderna, Inc.