COVID Vaccine Comparison

Scientists reveal key differences in immune response to inactivated COVID-19 virus and mRNA vaccines

New study reveals key differences in immune responses of inactivated SARS-CoV-2 vaccines and COVID-19 spike mRNA.

Although both protect against serious diseases, inactivated

SARS-CoV-2
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the official name of the viral strain that causes coronavirus disease (COVID-19). Before this name was adopted, it was commonly referred to as the 2019 novel coronavirus (2019-nCoV), Wuhan coronavirus, or Wuhan virus.

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“Inactivated SARS-CoV-2 vaccines were used extensively in Asia, but are often considered inferior due to their induction of a lower antibody response compared to other types of vaccines,” said Dr. Anthony Tanoto Tan, senior co-author of the study. “This means that they might not have been as good at preventing infection, but several studies have shown that they are highly capable of thwarting the development of severe COVID-19.” Tan is a Senior Research Fellow with the Duke-NUS’ Emerging Infectious Diseases (EID) Program.

Four COVID-19 vaccines are approved or authorized in the United States by the FDA: Pfizer-BioNTech, Moderna, Novavax, and Johnson & Johnson’s Janssen (J&J/Janssen). Pfizer-BioNTech and Moderna are Messenger

However, unlike the mRNA vaccines, the inactivated virus vaccines did not appear to trigger cytotoxic CD8 T cells known for their ability to kill virus-infected cells. They mainly stimulated a type of T cells called CD4 T helper cells. When these T cells recognize a viral antigen, they release chemicals, called cytokines that help the activation of other types of immune cells, hence their name.

Senior author of the study Professor Antonio Bertoletti from Duke-NUS’ EID Program said: “The Omicron variant can effectively evade antibody neutralization, moving the evaluation of vaccination efficacy away from preventing infection and towards ameliorating disease. T cells are likely to play a more important role in this compared to antibodies, due to their ability to target virus-infected cells.

“Since inactivated SARS-CoV-2 vaccines can generate T cell responses towards other viral proteins, this more heterogenous response could be beneficial, in comparison to the current Spike targeting strategy of other vaccines. However, larger studies are needed to clarify the impact of these T cells responses in SARS-CoV-2 pathogenesis to better design vaccines for controlling severe COVID-19 after infection by Omicron or future variants.”

To dig deeper into the implications of the different T-cell responses, the scientists called for further research with larger numbers of participants, to compare the ability of the multi-protein CD4 T-cell response induced by inactivated virus vaccines with that of the single spike protein coordinated CD4 and CD8 T cell response induced by mRNA vaccines to ameliorate COVID-19 disease severity.

Reference: “A comparative characterization of SARS-CoV-2-specific T cells induced by mRNA or inactive virus COVID-19 vaccines” by Joey Ming Er Lim, Shou Kit Hang, Smrithi Hariharaputran, Adeline Chia, Nicole Tan, Eng Sing Lee, Edwin Chng, Poh Lian Lim, Barnaby E. Young, David Chien Lye, Nina Le Bert, Antonio Bertoletti and Anthony T. Tan, 5 October 2022, Cell Reports Medicine.
DOI: 10.1016/j.xcrm.2022.100793


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