A study conducted by the University of Gothenburg reveals promising results for even vulnerable individuals, those at high risk of severe COVID-19, who received three doses of mRNA vaccine. Patients who had undergone a bone marrow transplant or had liver disease, including cirrhosis, demonstrated strong antibody levels in response to the vaccination.

The objective of the study, published in Infectious Diseases, was to explore the impact of repeated vaccinations and hybrid immunity on COVID-19 among individuals considered particularly vulnerable. Hybrid immunity, a combination of protection from vaccination and previous SARS-CoV-2 infection, was also investigated during the research.

The findings illustrate the gradual increase in COVID-19 antibodies with each successive vaccine dose in individuals with a compromised immune system. This area of research still lacks comprehensive understanding and knowledge.

Equivalent After the Third Dose

The research involved 38 patients with liver cirrhosis, 36 bone marrow transplant recipients, 14 patients with autoimmune liver disease, and 20 healthy controls. All individuals received care at Sahlgrenska University Hospital in Gothenburg, Sweden.

After receiving their first, second, and third vaccine doses, the patients’ COVID-19 antibody levels were closely monitored. For some bone marrow transplant recipients, they were monitored even after their fourth vaccine dose. Before the second dose, none of the participants had experienced COVID-19. However, between the second and third doses, 31 of them had a mild COVID-19 infection caused by the omicron variant.

Until the second dose of the vaccine, individuals with compromised immune defense, such as those with liver disease or who had undergone a bone marrow transplant, had lower levels of protection compared to the control group. However, after receiving the third dose, all groups exhibited similar levels of antibodies.

Irrespective of their initial level of underlying immunity, all groups participating in the study demonstrated antibody levels that were 10 times higher after acquiring COVID-19 infection compared to those who had gained immunity solely through vaccination.

Unexpectedly Good Protection Among the Vulnerable

The administration of three doses of mRNA vaccine against COVID-19 led to significant increases in antibody concentrations, even among immunocompromised individuals. Moreover, the combination of vaccination and prior infection (hybrid immunity) resulted in even higher levels of antibodies.

“It was unexpected but extremely pleasing to note that vulnerable individuals achieved antibody levels on a par with the healthy ones after three doses of vaccine. This underlines the importance of continuing to vaccinate, even if the immune response is poor after the first doses,” says last author Martin Lagging, MD, PhD, professor in clinical virology at the University of Gothenburg’s Sahlgrenska Academy and a senior physician at Sahlgrenska University Hospital, in a release.