Finnish researchers have provided reassuring news that COVID-19 infection does not harm the long-lasting immunological memory brought about by vaccines. This discovery addresses widespread concerns that coronavirus might permanently weaken the immune defense system, similar to the way measles virus can impair immunological memory.

Published in peer-reviewed scientific journals, Pathogens and Immunity and Virus Research,

the studies by the University of Helsinki researchers explore the effects of COVID-19 on the immune system. Unlike measles, which is known to infect and kill white blood cells, leading to diminished immunological memory for vaccines received in childhood, COVID-19's impact appears to be different.

Eliisa Kekäläinen, part of the research team, notes that while certain white blood cells, crucial for viral defense, are reduced during acute COVID-19, particularly in severe cases, this does not result in the same type of immunological damage as measles. Specifically, a subtype of T-cells associated with mucosal defense, known as MAIT cells (Mucosal associated invariant T cells), was significantly reduced in severe COVID-19 cases. However, these cells were found in abundance in the lungs, suggesting their migration to the site of infection could explain their temporary reduction in the bloodstream.

The study also examined the effect of COVID-19 on antibody levels against vaccines for diseases such as tetanus, whooping cough, and diphtheria. If COVID-19 had caused damage similar to measles, a decrease in antibody levels would have been expected. However, the research found no change in antibody levels, even among hospitalized patients, indicating that COVID-19 does not directly damage cell- or antibody-mediated immune defense.

Interestingly, patients reporting prolonged changes in their sense of smell had lower levels of tetanus and diphtheria antibodies in the acute phase, but this was not seen as directly related to COVID-19 infection, as whooping cough antibody levels and overall antibody levels did not show the same pattern. This group was younger on average, suggesting they might not have received booster vaccinations like older patients.

This research, which covers a broad spectrum of COVID-19 cases, including those not requiring hospitalization, offers a more comprehensive view than previous studies focused solely on hospitalized patients. The findings are a relief, suggesting there's no need for additional vaccine boosters specifically due to COVID-19-related immune system damage. The study also indicates that the resurgence of infections post-pandemic restrictions is not linked to immunological damage caused by COVID-19.

Eliisa Kekäläinen's team plans to focus future research on patients with long-term COVID-19 symptoms, a group not covered in this study, to further understand the virus's long-term impacts on human health.