# COVID-19 and Influenza Booster Vaccination Elicits Robust Antibody Responses in Patients with Primary Brain Tumors Comparable to Healthy Adults

## TL;DR

This study shows that patients with brain tumors can develop strong antibody responses to booster vaccines for COVID-19 and influenza, similar to healthy adults.

## Contribution

The study demonstrates preserved recall immunity in brain tumor patients after booster vaccinations, challenging assumptions about their immune response.

## Key findings

- Median anti-SARS-CoV-2 Spike antibody titers increased significantly in brain tumor patients after booster vaccination, comparable to healthy controls.
- Brain tumor patients showed a significant increase in anti-Influenza IgG antibody titers after vaccination, similar to controls.
- Only two heavily pre-treated patients showed no booster response, indicating most patients can mount robust immune responses.

## Abstract

Patients with primary brain tumors experience substantial disease- and treatment-related immunosuppression. This study addresses a critical gap in understanding vaccine efficacy in this population. In this prospective cohort study, we evaluated serum antibody responses before and after seasonal mRNA COVID-19 and influenza booster vaccination in patients with primary brain tumors and healthy controls. The results demonstrate robust immune responses to the mRNA COVID-19 and seasonal influenza booster, comparable to those observed in healthy controls, indicating preserved recall immunity. Our findings provide a rationale to prioritize vaccination in this vulnerable population. The data challenge the notion that profound immunosuppression precludes effective recall immunity and support the inclusion of patients with primary brain tumors in future vaccine trials.

Background: Patients with primary brain tumors face profound disease- and treatment-related immunosuppression, placing them at high risk for severe infections. Their capacity to mount protective immune responses to vaccination, particularly to repeated antigen exposures such as COVID-19 boosters, remains critically under-defined, leading to uncertainty in clinical practice. Methods: In this prospective cohort study, we analyzed humoral responses to seasonal COVID-19 (mRNA-based) and influenza vaccination in 17 patients with primary brain tumors (recruited from an initial cohort of 37) who received a booster shot, and 19 healthy controls. Serum samples were collected before (T1) and 30 ± 2 days after (T2) vaccination to quantify SARS-CoV-2 anti-Spike (S) IgG and anti-Influenza IgG titers. Results: Despite ongoing chemotherapy in 47% of patients, baseline anti-S antibody titers were comparable between groups. Following the booster, median anti-S titers increased significantly and to a similar magnitude in both patients (from 5030 to 18,500 BAU/mL; IQR: 13,885–24,420) and controls (from 4429 to 20,200 BAU/mL; IQR: 11,075–26,680; p = 0.6137, Mann–Whitney U test). Only two heavily pre-treated patients showed no booster response. All participants showed sero-positivity to Anti-Influenza IgG at baseline. For the primary brain tumor cohort, a significant increase for anti-Influenza IgG at T2 was observed (p = 0.0002). Mean antibody titers did not differ between both cohorts. Conclusions: Our findings provide evidence that patients with primary brain tumors can mount robust recall immunity to mRNA vaccines, addressing clinical uncertainty about booster efficacy in this population. These data provide a strong rationale for prioritizing booster vaccinations in this vulnerable population and argue for the inclusion of these patients in future pivotal vaccine trials.