Researchers from Johns Hopkins have found that the mRNA Covid vaccines developed by Pfizer and Moderna not only work with the original strain of SARS-CoV-2, but also new variants, as well as the common cold.
After receiving either vaccine the immune system produces CD4+ T lymphocytes, immune cells also known as helper T cells. These cells activate another type of immune cell known as B lymphocytes (B cells) which respond to surface proteins on cells infected by viruses including SARS-CoV-2. Once activated in this way, immature B cells either become plasma cells that produce antibodies that mark infected cells for disposal, or ‘memory cells’ that help the body recognize and react to the same antigens more quickly in future infections.
For the study, the researchers examined blood samples from 30 healthy healthcare workers and lab donors who had not previously tested positive for COVID-19 before and after receiving a COVID-19 mRNA vaccine. They then withdrew CD4+ T cells from their blood samples and tested their response to protein fragments from the original SARS-CoV-2 spike protein as well as three common cold coronaviruses.
In doing so, they identified 23 distinct T cell-targeted peptides. From these, only four were affected by the mutations seen in COVID variants from the United Kingdom and South Africa. As the other 19 peptides which are targeted by the vaccines are the same in both the original virus and the newer strains, the mRNA vaccines should theoretically induce T cells that respond to these variants too.
The researchers say this means that the T cells induced by mRNA vaccines may prevent the variant viruses from causing severe cases of COVID-19 disease, even if they don’t prevent infection. They also noted that the vaccines led to a three-fold increase in CD4+ T cell responses to HCoV-NL63 spike peptides after vaccination, meaning that the vaccine should also work for a variant of the common cold.