New study: mRNA vaccines may affect fetus during pregnancy

A new study has revealed that mRNA vaccines may be dangerous for unborn children because they reach the fetus directly through the mother's body.

Example of a specific mRNA case

In 2020, the COVID-19 pandemic spurred the development of mRNA vaccines to protect against the virus, but their emergence has raised many questions, including the safety of the Moderna vaccine.

However, it was stated at the time that these types of vaccines were generally safe, even for pregnant women. On the other hand, it was not yet clear how they would work when they crossed the placenta and entered the body of the unborn child.

A study published by Taiwanese scientists   suggests that such vaccines can cross the placenta and reach the fetuses of pregnant mice. 

Scientists note that this process is also common in humans, but the long-term consequences after birth are still unknown.

Potentially accumulated in tissues 

According to a new study, the mRNA-1273 vaccine injected intramuscularly into pregnant mice rapidly entered the mother's bloodstream and crossed the placenta into the fetal bloodstream within one hour, leading to some severe effects after birth.

"This type of vaccine has had a good safety profile in clinical practice, including in pregnant women. However, the positive safety results in clinical practice have not eliminated concerns about potential genotoxicity, such as genome integration, oncogenesis, or hereditary transmission, which arose after long-term distribution of the mRNA vaccine or its product in the body was detected in pre-marketing studies," the study authors said.

Although the spike protein mRNA detected in the fetal bloodstream disappeared within 4–6 hours, it could accumulate in fetal tissues, especially the liver, and be converted to spike protein, which can cause various abnormalities.

No comprehensive preclinical studies have been performed. 

The researchers also emphasized that these "uncomfortable" findings were overlooked due to the hasty approval of mRNA vaccines for the market, without thorough preclinical testing during the pandemic.

"Given the cases of retrointegration of SARS-CoV-2 RNA into the genome of human cells, a long-term risk of genotoxicity in children born to mothers vaccinated with the mRNA vaccine cannot be excluded," the researchers noted.

Based on the results of the study, scientists gained new insights into the transplacental pharmacokinetics of this type of vaccine and the immunogenic effect of the mRNA-encoded protein in fetuses.

This may help advance knowledge on how to better protect unborn children from pathogens during the perinatal period in the modern era of mRNA medicine.