The two vaccines based on ribonucleic acid molecules (mRNA vaccines), approved for the COVID-19 vaccination campaign, work by delivering a small segment of mRNA into some cells of the vaccinated person. This mRNA segment contains the instructions for temporarily producing the spike protein, a protein found on the surface of coronavirus SARS-Cov-2.
In these vaccines, the small viral mRNA segment is embedded in microscopic lipid particles that, by merging with human cells, deliver such segment into the cells. Here, the viral mRNA segment starts the temporary production of the spike proteins. The person’s immune system will recognise these proteins as foreign and will activate lymphocytes and produce antibodies.
After the vaccination, some of the lymphocytes that acted against the spike protein will survive for several months. The presence of these ‘memory lymphocytes’ will enable the person’s immune system to rapidly activate a formidable response against a possible invasion of the virus responsible for COVID-19.