Scientists from Harvard University found that vaccines induce multiple immune system mechanisms to protect against severe COVID-19 illness.
They found that while vaccine-induced neutralizing antibody responses protect against infection, control of viral replication is mediated by responses that involve T cells and the antibody-binding receptor.
The research is published in PLOS Biology and was conducted by Galit Alter et al.
Globally, breakthrough COVID-19 infections among vaccinated people are increasing, raising concerns about the durability of protection against emerging, highly contagious variants of concern.
While vaccine-induced neutralizing antibody responses (that is, antibodies that directly bind the virus and “neutralize” infection) provide the primary protection against infection and severe disease, other, less well understood, immune responses contribute to protection.
In the study, the team examined the protective role of each immune mechanism.
They immunized five groups of five monkeys with different doses of COVID-19 vaccine or a sham control.
They then challenged all monkeys with COVID-19 infection and analyzed viral replication in the upper and lower respiratory tracts 1, 2, 4, 7 and 10 days after the viral challenge.
The researchers found that the immunity mechanisms responsible for controlling viral replication following infection were dose dependent, indicating an important role in protection against severe illness and death.
These additional immune responses which control viral replication are mediated by the so-called Fc receptor and by T-cell responses, complementing the other antibody responses that directly neutralize the virus.
The team says the continued emergence of several SARS-CoV-2 variants with enhanced infectivity and immune evasive capacity has further complicated the worldwide vaccination effort.
The current findings provide critical insights into the context of the current pandemic.
Emerging variants of concern have the capability of breaking through vaccine-mediated protection, but vaccine-induced immunity still elicits a response against several variants and provides some level of protection against severe disease and death.
If you care about COVID, please read studies about new treatment option for COVID-19, and COVID-19 booster provides stronger, longer protection than original vaccines.
For more information about COVID, please see recent studies about a universal antibody therapy for all COVID-19 variants, and results showing scientists find persistent immune inflammation after mild COVID-19.
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