According to a study, the second dose of a COVID-19 vaccine provides a powerful boost to the part of the immune system that provides widespread antiviral protection. A team of researchers from Stanford University School Medicine set out to determine the precise impact of the vaccine on the numerous components of the immune response.
The study, published in Nature, looked at blood samples from individuals vaccinated with the vaccine.
Blood was collected from 56 healthy volunteers at multiple time points prior to and following the first and second shots.
Researchers noted that the first injection increases COVID-19-specific antibody levels, but not nearly as much as the second.
Bali Pulentran, PhD, professor of pathology and microbiology and immunology said: “The second injection has potent beneficial effects that are much greater than those of the first injection.
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“It stimulated a multiple-fold increase in antibody levels, a great T-cell response that was absent after the first injection alone, and a markedly enhanced innate immune response.”
Pulendran and his team assessed the activity of the immune cells affected by the vaccine.
They counted antibodies and measured levels of immune signaling protein.
The researchers observed that immune cells that do not attach to viral particles as antibodies, but rather examine the body tissue for signs of viral infection. When they find them, they tear those cells apart.
Pulendran said: “The world’s attention has recently been drawn to COVID-19 vaccines, especially the new RNA vaccines.
“This is the first time RNA vaccine has ever been given to humans, and we have no idea how they do what they do: provide 95% protection against COVID-19.
“Despite our excellent efficacy, little is known about exactly how RNA vaccines work.”
The immunological basis for the approval of vaccines is their ability to induce neutralizing antibodies that can attach to a virus and prevent it from infecting cells.
Pulendran emphasized the importance of the innate immune system in fighting infections.
He explains that the “sixth sense of the body” is now considered to be of enormous importance.
He added: “Antibodies are easy to measure, but the immune system is much more complicated than that. Antibodies alone don’t come close to fully reflecting the complexity and potential range of protection.”
During the week or so it takes for the adaptive immune system to kick in, innate immune cells perform the mission-critical job of keeping infection at bay by gobbling down anything they think is a pathogen.
The findings come as every adult in the UK has received a first dose of a COVID-19 vaccine, reaching the prime minister’s target ahead of schedule.
More than 82,413,766 doses have been administered in the UK, with 87.9 percent receiving a first dose and 68.5 percent receiving both vaccines.
Data from Public Health England (PHE) shows that COVID-19 vaccines are highly effective against hospitalizations of the Delta variant.
The analysis shows that the Pfizer-BioNTech has a 96 percent effect and the Oxford-AstraZeneca vaccine is 92 percent effective against hospitalizations after two doses.