Immune Cells Against COVID-19 Stay High in Number Six Months After Vaccination, Study Shows

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Study Shows Immune Cells Against Covid-19 Stay High in Number Six Months After Vaccination:

"Previous research has suggested that humoral immune response - where the immune system circulates virus-neutralizing antibodies - can drop off at six months after vaccination, whereas our study indicates that cellular immunity - where the immune system directly attacks infected cells - remains strong," says study senior author Joel Blankson, M.D., Ph.D., professor of medicine at the Johns Hopkins University School of Medicine. "The persistence of these vaccine-elicited T cells, along with the fact that they're active against the delta variant, has important implications for guiding COVID vaccine development and determining the need for COVID boosters in the future."

To reach these findings, Blankson and his colleagues obtained blood from 15 study participants (10 men and five women) at three times: prior to vaccination, between seven and 14 days after their second Pfizer/BioNTech or Moderna vaccine dose, and six months after vaccination. The median age of the participants was 41 and none had evidence of prior SARS-CoV-2 infection.

[...] In their study, Blankson and colleagues found that the number of helper T cells recognizing SARS-CoV-2 spike proteins was extremely low prior to vaccination - with a median of 2.7 spot-forming units (SFUs, the level of which is a measure of T cell frequency) per million peripheral blood mononuclear cells (PBMCs, identified as any blood cell with a round nucleus, including lymphocytes). Between 7 and 14 days after vaccination, the T cell frequency rose to a median of 237 SFUs per million PBMCs. At six months after vaccination, the level dropped slightly to a median of 122 SFUs per million PBMCs - a T cell frequency still significantly higher than before vaccination.

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