188P - Efficacy of SARS-CoV-2 based mRNA vaccines for patients with thoracic malignancies with 6 months follow up: A prospective observational study

Background

Vaccination against SARS-CoV-2 in patients (pts) with thoracic malignancies is crucial since they are at high risk of having severe COVID-19 disease course. Still, data on efficacy of vaccination in this pt population are scarce.

Methods

Prospective observational study of pts with solid cancers on active anticancer treatment (chemotherapy, immunotherapy with immune checkpoint inhibitors (ICI) or targeted therapy (TT)) that received mRNA-based SARS-CoV-2 vaccination was performed. Pts were sampled before, 2-3 weeks after the first, 2-3 weeks after the second dose, 3 and 6 months after the complete primary course of vaccination. Detection of anti-SARS-CoV-2 S1 IgG antibodies in serum was determined with commercial ELISA assay IDK®. Samples with ≥ 175 ng/ml were considered positive. Here we present data on pts with thoracic malignancies.

Results

Ninety-two pts were included in the analysis. Median age at diagnosis was 63 years, 49% were female and 93% were currently receiving anticancer therapy. Pts were treated for NSCLC, SCLC and malignant pleural mesothelioma in 90%, 5% and 5%, respectively. Eighteen pts had previous exposure to COVID-19. Out of 74 COVID-19 naïve pts, seroconversion after 1^st vaccination was 61%, after 2^nd 96%, and seropositivity 3 and 6 months after 2^nd vaccination 94% and 95%, respectively. According to treatment type, pts treated with chemotherapy, chemo + ICI, ICI alone or TT achieved seroconversion after 2^nd vaccination in 100%, 83%, 96% and 100%, and mostly maintained positive levels of anti-SARS-CoV-2 S1 IgG antibodies 6 months after 2^nd vaccination with 100%, 100%, 89% and 95%, respectively. However, there was a marked decrease in anti-SARS-CoV-2 S1 IgG antibody level of 69% in average 3 months after and 80% in average 6 months after the 2^nd vaccination in pts with thoracic malignancies (both P < 0.001).

Conclusions

Pts with thoracic malignancies achieve high proportion of seroconversion after two doses of mRNA-based vaccines, yet, anti-SARS-CoV-2 S1 IgG antibody levels decline substantially 3 and 6 months after the 2^nd vaccination, thus the 3^rd dose of vaccine is reasonable to provide adequate protection against severe COVID-19 disease course.

Legal entity responsible for the study

The authors.

Funding

Slovenian Research Agency (Grant no. P3-0360).

Disclosure

All authors have declared no conflicts of interest.