Person receiving a COVID-19 vaccine. LEHTIKUVA / AFP

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Recent research at the University of Turku in Finland indicates that COVID-19 vaccines provide a lasting defense against serious illness caused by various coronavirus strains, primarily through T-cell activation. This significant finding emerges amidst the ongoing battle against the COVID-19 pandemic, which, unlike previous influenza pandemics, has spread rapidly worldwide and witnessed the swift emergence and spread of new variants.

The dissertation by Turku University's researcher, Pinja Jalkanen, focused on examining the immunity conferred by both COVID-19 vaccines and natural infection against the virus variants circulating in Finland during 2020 and 2021. The study used samples collected from COVID-19 patients and the staff of university hospitals in Turku and Helsinki at the onset of vaccinations in Finland.

Jalkanen emphasizes the critical importance of monitoring immunity produced by vaccinations. This monitoring helps evaluate the vaccine's effectiveness, the durability of immune protection, and the need for booster doses. According to the study, vaccination led to the formation of antibodies against the virus's spike protein, effectively preventing infection by the vaccine virus and the Alpha variant in cell cultures. However, these antibodies were slightly less effective against more mutated Beta and Delta variants.

Notably, serum samples from vaccinated individuals, as well as those who had recovered from COVID-19 and then got vaccinated, neutralized all virus variants more effectively compared to those who had only recovered from the illness. The vaccinations induced a robust antibody response against the coronavirus variants prevalent at the start of the pandemic.

A key observation of the study was that while virus mutations did not significantly impact cell-mediated immunity, vaccinations not only produced antibodies but also activated T-cell-mediated immunity. T-cells play a crucial role during the recovery phase of the disease by destroying virus-infected cells and protecting against severe forms of coronavirus infection. Unlike antibodies, whose levels declined a few months after vaccination, T-cells recognizing the coronavirus were found in the bloodstream for up to six months post-vaccination without a decrease in their numbers over the observation period.

Jalkanen notes that while the exact amount of antibodies required to protect against breakthrough infections remains unknown, the robust T-cell response generated by the vaccines likely provides substantial protection against severe forms of COVID-19.

The findings indicate that mRNA COVID-19 vaccines elicit an excellent antibody and cell-mediated immune response, suggesting that these vaccines offer long-lasting protection against severe forms of COVID-19.

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