COVID mRNA vaccines display weakened immune response

The BNT162b2 vaccine produced by Pfizer, as well as the mRNA-1273 vaccine produced by Moderna, both work on the same principle. To that end, they are both messenger ribonucleic acid (mRNA) vaccines that produce immunity by delivering the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein mRNA to the cell.

The cellular machinery then translates the mRNA, thus leading to the production of the protein. This ultimately allows the immune system to mount a robust immune response against SARS-CoV-2. As no viral structural proteins are involved in this process and the mRNA is non-infectious and non-integrative, this approach is considered safer than traditional vaccines created from inactive strains of the virus, which can reactivate or cause allergic reactions.

Following observations in alternative vaccines showing weak immunity in the elderly, researchers at Simon Fraser University in Canada decided to study the extent of this effect in mRNA vaccines against COVID-19. . In total, these researchers looked at responses from 151 people, including healthcare workers, the elderly, and people living in long-term care facilities and assisted living facilities.

Serum and plasma were collected from these individuals before vaccination, one month after the first dose and three months after the second dose. Those who were infected with SARS-CoV-2 at the start of the study were identified by the presence of antibodies recognizing the SARS-CoV-2 nucleoprotein.

A pre-printed version of this study is currently available on the medRxiv* server.

To examine the immune response, the scientists performed binding antibody assays against the SARS-CoV-2 nucleoprotein and spike protein receptor binding domain (RBD), as well as quantified the response of the immunoglobulin G (IgG) beads using enzyme-linked immuno-absorbent assays (ELISA).

SARS-CoV-2 enters human cells by binding its spike protein RBD to the angiotensin-converting enzyme 2 (ACE2) receptor on the host cell. Thus, this interaction is an important aspect of vaccine-mediated immunity, as vaccine efficacy is often measured by the ability of plasma antibodies to block this interaction.

Binding between SARS-CoV-2 RBD and ACE2 receptors was measured by competition ELISA, where bound ACE2 was detected using streptavidin-PE. Neutralizing antibody activity was detected by assays for viral cytopathic effect, which describes virus-induced death of the cell by lysis or inability to reproduce.

The researchers found that after the first dose, median anti-RBD IgG titers were 4.2 times lower in elderly people than in healthcare workers. The exception to this were the 14 people who had been infected with SARS-CoV-2 before being vaccinated, who showed IgG responses between 190 and 840 times higher, a finding supported by previous studies showing a response intense immunity to COVID -19 in people who have already been infected and who have received a dose of the COVID-19 vaccine.