vaccine Photo: VCG

The large-scale use of mRNA-based COVID-19 vaccines including those produced by Pfizer and Moderna may contain unknown risks, Chinese experts warned, and called for the cautious use of such vaccines following the death of a patient in the US. 

Unlike inactivated vaccines, the large-scale use of mRNA vaccines carries the risk of causing abnormal immune dysfunction, allergy or even death especially among the elderly and people with underlying diseases, the Chinese immunologist said, while some observers call for more investigation over the death before drawing a conclusion that mRNA vaccines are unsafe. 

The patient, from Placer county, California, died hours after receiving a coronavirus vaccine, triggering concerns over the safety of mRNA vaccines, despite Placer county officials rejecting the link between the person's death and the vaccine, KTLA reported.  

Officials did not reveal where the patient received the shot and which vaccine was used in this particular case, the report said. 

The vaccines that the county received were likely either the Pfizer-BioNTech COVID-19 vaccine or Moderna COVID-19 vaccine, as the two had been authorized in the US for application. The two are both mRNA vaccines.

California authorities are investigating the cause of death. 

A Beijing-based immunologist, who requested anonymity, told the Global Times on Monday that some components in mRNA vaccines, such as polyethylene glycol (PEG), have not been used in vaccine production before, and it is no surprise to see allergic reactions in some people. The liposome physical properties of the vaccine also carry the risk of causing abnormal immune function disorders. 

The mRNA vaccines teach human cells to make a protein to trigger an immune response, which can then protect people from getting infected if the real virus enters the body. 

He called on suspension of the use of the mRNA COVID-19 vaccines on the elderly and people with underlying diseases, as this new technology has not proven to be safe in large-scale use.

Previously, Norway reported the deaths of 23 elderly Norwegian people who received mRNA-based COVID-19 vaccines. All the deaths occurred in frail, elderly patients in nursing homes. All were over 80 years old and some of them over 90, Norwegian media NRK reported.

However, Lü Mengtao, a medical industry observer, told the Global Times on Monday the reported death may not be directly related to the vaccines which should be assessed cautiously so that the mRNA vaccine being deemed unsafe is not made irrationally.

The observer suggested individuals with preexisting conditions of disease, the elderly, and those with vulnerable immunity not to have such vaccines injected.

Even for inactivated vaccines with more mature technology, those high-risk groups such as the elderly and people with underlying diseases are not advised to be administrated immediately. 

Global Times