Preliminary results of the study vaccine COVID-19 in mice American company Moderna show that it does not increase the risk of a more severe course of the disease and that one dose can provide protection from COVID-19, the study, published Friday in the online bioRxiv, posting scientific materials.
Previous studies of vaccines against viruses close to SARS-CoV-2 have shown that vaccines against this type of infection can have the effect of causing a more severe course of the disease when the vaccinated person is subsequently exposed to the pathogen, especially in people with weak immunity. This risk is considered to be a significant obstacle that needs to be addressed before vaccines can be safely tested on thousands of healthy people.
According to the study, scientists administered various amounts of the vaccine to six-week-old mice, including doses considered not strong enough to trigger a protective immune response. The researchers then exposed the mice to the virus.
As the scientists emphasize, the preliminary data obtained showed that the vaccine is a “powerful mutagenic substance,” and neutralizing activity “can be achieved with a single dose.” Also, it is noted that “subproective doses did not lead to increased immunopathology” after exposure to the virus in mice, that is, they did not cause a more severe course of the disease.
Further testing showed that the vaccine elicits a robust response to neutralizing antibodies. This is what is needed to block the virus so that it does not infect cells. The vaccine also protects the lungs from coronavirus infection without signs of toxic effects.
Data on mice published by the US National Institute of Allergy and infectious diseases and Moderna, however, do not guarantee that the same results will be obtained in human studies.
Moderna said on Thursday that it plans to start the final stage of testing in July, which will be attended by 30,000 people.
In early March, the WHO declared the coronavirus outbreak a pandemic. In total, more than 7.4 million people were infected with it in the world, and more than 418 thousand died.