Booster doses of mRNA vaccines improve humoral immunogenicity in patients with inflammatory bowel disease

In response to the ongoing coronavirus disease 2019 (COVID-19) pandemic, the regulatory bodies gave emergency approvals to three safe and effective COVID-19 vaccines for mass vaccination programs. Neither patients with inflammatory bowel disease (IBD) nor immunosuppressed patients were included in the original Phase III clinical trials conducted to prove vaccine efficacy.

Studies conducted later with IBD patients have demonstrated a humoral immune response rate of 95–99% following vaccination with a double dose of different mRNA vaccines. Results also showed that patients on certain immune-modifying therapies, such as anti-tumor necrosis factor (anti-TNF) therapy in combination with an immunomodulator, or on systemic corticosteroids, exhibited a relatively diminished humoral immune response. They also underwent a relative reduction in serum antibody concentrations over time.

The Advisory Committee on Immunization Practice (ACIP) recommends a three-dose primary mRNA vaccine series for patients who are moderately or severely immunocompromised, keeping the reduced antibody-titers in mind.

Researchers recently published a study in the preprint server medRxiv* wherein they evaluated the humoral immunogenicity of a third COVID-19 mRNA vaccine dose in patients with IBD. They had further hypothesized that the patients would mount a significant humoral immune response and that those on certain immunomodulating therapy, like systemic corticosteroids or combination therapy, may have lower antibody concentrations.

Study details

The study was a multi-center, prospective, non-randomized study, known as the “HumoRal and CellULar initial and Sustained immunogenicity in patients with IBD” (HERCULES) study.  Participants with IBD were enrolled at the University of Wisconsin-Madison (Madison, Wisconsin) and Mayo Clinic (Jacksonville, Florida), while healthy controls (HC) were employees of LabCorp.

The eligibility criteria for patients included a diagnosis of IBD, age 18–85 years, stable doses of maintenance therapy (≥ 2 months), vaccination with a double-dose mRNA vaccine, as confirmed by interview, review of medical records, and if applicable, review of the Wisconsin Immunization Registry. The eligibility criteria for the controls (HC) included the absence of immunosuppressive therapy and documented evidence of a double-dose mRNA vaccination. A third COVID-19 mRNA vaccine dose was available only for patients with IBD. The primary study outcome was total serum SARS-CoV-2 anti-spike IgG antibody concentrations following a third dose compared to antibody concentrations following the conventional double-dose series in the IBD cohort.

Serum IgG antibodies specific to nucleocapsid and spike protein S1 receptor-binding domain (RDB)- were reported in mcg/ml. In patients with IBD, antibody concentrations were measured between 28 and 35 days (t1) after completion of the double-dose series and between 28 and 65 days (t2) after the third dose. Only patients with IBD who received a third dose had antibody concentrations measured at t2, and not every subject who had antibody concentrations measured at t2 had them measured at t1 due to timing of enrolment. In the control group, antibody concentrations were measured at 30 days (t1) and 180 days (t2) after completion of the double-dose series.

The study included 139 patients with IBD who had competed the double-dose regime and had antibody concentrations measured at t1, and 85 patients who received a third dose and had antibody concentrations measured at t2. Fourty-six HC completed the double-dose regimen and had antibody concentrations measured at both time points. In the IBD cohort, 48.2% and 51.8% received the double-dose Moderna and Pfizer series, respectively, compared to 93.5% and 6.5% in HC.

135 patients with IBD (97.1%) had detectable antibody concentrations at t1, while all 85 (100%) had detectable antibody concentrations at t2. Of the 2 patients with IBD who were seronegative at t1 and received a third dose, each had detectable antibody concentrations (mean 6.25 µg/mL, SD 2.1) at t2; one subject was on anti-TNF monotherapy and the other was on tofacitinib. At t2, antibody concentrations were similar between patients with IBD on immunosuppressive therapy and non-immunosuppressive therapy (median 69 vs 66). Further subgroup analysis revealed that those on systemic corticosteroids or anti-TNF combination therapy had significantly lower antibody concentrations at t2 than patients that were not on these therapies (median 29 vs. 7)

When adding those on anti-TNF monotherapy to the former group, the difference in median antibody concentrations was reduced but remained statistically significant (median 38 vs. 73). Serum antibodies were significantly higher at t2 for patients with IBD who received three doses of the Moderna vaccine compared to those who received the same in Pfizer (median 94 vs. 62).

Although the control group had higher antibody concentrations compared to IBD subjects at t1 (median 120 vs. 31), their antibody concentrations fell significantly below that of the IBD cohort at t2 (median 17 vs. 68).

Implications

All patients were seropositive and had higher antibody concentrations after the third dose than after completion of the two-dose primary series. This adds to the growing body of evidence regarding the booster doses of vaccines. This would also help entailing more studies on different populations of immunocompromised patients, as well as help policymakers in defining their booster dosing criteria for the general public.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Sreetama Dutt

Sreetama Dutt has completed her B.Tech. in Biotechnology from SRM University in Chennai, India and holds an M.Sc. in Medical Microbiology from the University of Manchester, UK. Initially decided upon building her career in laboratory-based research, medical writing and communications happened to catch her when she least expected it. Of course, nothing is a coincidence.