Blog: coronavirus vaccine protection – weakening and vulnerable or strong and sustainable?

Mika Rämet 
Professor of Paediatrics and Experimental Immunology ​ 

Compared with the previous coronavirus variants, the Omicron variant requires a much greater concentration of neutralising antibodies produced by coronavirus vaccines to prevent the virus from entering the cell. Without these antibodies, breakthrough infections will begin to appear among vaccinated people just a few months after the most recent vaccine dose. Should we therefore get vaccinated against the coronavirus again and again, at only a few months’ intervals? 
 

Spike protein evades antibodies 

Immunity, or the body’s natural resistance to disease, consists of several components. In the best case, the antibodies on mucous membranes prevent the virus from entering the cells, in which case exposure does not lead to symptoms. To spread among the population, the virus needs to bypass this protection. For example, the coronavirus has evolved so that the spike protein in the Omicron variant evades the antibodies generated by the coronavirus vaccines that optimally recognise the original coronavirus. This enables the virus to enter cells and cause a respiratory infection. Does this mean that coronavirus vaccines have become ineffective? 
 

Long-term immunity based on memory cells 

Coronavirus vaccines activate the body’s immune response more extensively than just by triggering the production of antibodies. Vaccines also activate cell-mediated immunity to recognise cells infected by the virus. In addition, vaccines leave an imprint on memory cells that lasts for years. The memory cells rapidly trigger an immune response when they encounter the spike protein again. 

Studies show that the cell-mediated immunity generated by coronavirus vaccines also works effectively against the Omicron variant. The memory cells that remain in the body after vaccination (or infection) have been shown to recognise several areas of the spike protein. This is why these memory cells, which trigger the production of antibodies, respond quickly to different variants of the coronavirus. In the animal model, the original mRNA vaccine has generated a level of protection as effective as a vaccine tailored to the Omicron variant. 

Based on these results, the findings from the Finnish data are not surprising: three doses of the vaccine have provided practically 100% protection for people aged 18–69 with good general health against coronavirus infections caused by the Omicron variant that require hospital treatment. 

Coronavirus vaccines are highly effective, with long-term protection. In preventing severe infections by means of vaccines, fourth doses for working-age people with good general health are not urgent.

​Text: Mika Rämet