It is possible to change the DNA of a cell to make changes in protein expression. There are several methods, some low cost like using a virus vector [0], some much more complex and costly. See for example the Astrazeneca candidate vaccine [1] which creates spike-specific antibodies.
[0] https://en.wikipedia.org/wiki/Vectors_in_gene_therapy
[1] https://en.wikipedia.org/wiki/COVID-19_vaccine#Vaccine_candi...