A study from Stanford University, published in Cell, has found that vaccine mRNA and spike protein persist in lymph nodes for up to two months following the second vaccine dose. This is in contrast to what happens following infection, where spike protein was found only rarely.
In contrast to disrupted germinal centres in lymph nodes during infection, mRNA vaccination stimulates robust germinal centres containing vaccine mRNA and spike antigen up to eight weeks postvaccination in some cases…
The observed extended presence of vaccine mRNA and spike protein in vaccinee lymph node germinal centres for up to two months after vaccination was in contrast to rare foci of viral spike protein in COVID-19 patient lymph nodes… COVID-19 patient lymph nodes showed lower quantities of spike antigen.
The researchers also found the concentration of spike protein in the blood following vaccination was similar to that during infection.
At least some portion of spike antigen generated after administration of BNT162b2 becomes distributed into the blood. We detected spike antigen in 96% of vaccinees in plasma collected one to two days after the prime injection, with antigen levels reaching as high as 174 pg/mL. The range of spike antigen concentrations in the blood of vaccinees at this early time point largely overlaps with the range of spike antigen concentrations reported in plasma in a study of acute infection, although a small number of infected individuals had higher concentrations in the ng/mL range. At later time points after vaccination, the concentrations of spike antigen in blood quickly decrease although spike is still detectable in plasma in 63% of vaccinees one week after the first dose.
The researchers found evidence of ‘original antigenic sin’ from the vaccines, where a person vaccinated and then infected with a variant develops a weaker antibody response to that variant than an unvaccinated person infected with the variant. They describe it as a “strong imprinting effect of prior vaccination”.