Hybrid immunity improves the immune response after fourth Covid-19 vaccine dose in individuals with medical conditions predisposing to severe Covid-19

Abstract

BackgroundData on Covid-19 booster vaccinations and subsequent infections on immune responses in the immunocompromised is limited. We studied antibody responses after the fourth dose and subsequent breakthrough infection to define patient groups benefiting most from boosters.MethodsIn Finland, fourth vaccine (booster) doses were first recommended for severely immunocompromised individuals, whom we invited to participate in 2022. We assessed spike protein specific IgG antibody levels and neutralizing antibodies (NAb) against the ancestral and Omicron BA.1 strains one month after the fourth dose from 488 adult participants and compared to the levels of 35 healthy controls after 3 doses. We used Bayesian generalized linear modelling to assess factors explaining antibody concentrations after the fourth dose. We assessed vaccine-induced and hybrid immunity six months after the last vaccine dose.ResultsChronic kidney disease (CKD) and immunosuppressive therapy (IT) were identified as factors explaining sub-optimal antibody responses. The proportion of participants with a normal antibody response and NAbs were significantly lower in CKD patients as compared to controls. By the 6-month sampling one third of the participants became infected, which enhanced antibody levels notably in most immunocompromised participants.ConclusionsImpaired antibody responses, especially NAbs against the Omicron lineage, predict limited protection in individuals with CKD, and highlight the need for alternative pharmaceutical preventive strategies. Vaccination strategies should take into account development of robust hybrid immunity responses also among the immunocompromised.