Neutralizing activity against Omicron subvariants BA.1, BA.2, and BA.4/5 following the third SARS-CoV-2 vaccination in cancer patients undergoing chemotherapy.

OBJECTIVES

Despite the availability of bivalent vaccines targeting both the ancestral SARS-CoV-2 strain and Omicron subvariants, vaccination rates remain low in South Korea. This study aims to evaluate the neutralizing activity against Omicron subvariants following the third SARS-CoV-2 vaccination in patients undergoing chemotherapy, as well as to assess the need for additional vaccinations.

METHODS

Between April and November 2022, the authors assessed the neutralizing activity of the third SARS-CoV-2 vaccine dose in 63 patients undergoing chemotherapy using an ELISA-based surrogate Virus Neutralization Test (sVNT). The authors examined the influence of factors such as prior COVID-19 infection, cancer type (solid vs. hematologic malignancy), type of chemotherapy regimen (cytotoxic chemotherapy, targeted therapy, immune checkpoint inhibitors), and vaccine type (homologous vector, homologous mRNA, heterologous) on neutralizing activity.

RESULTS

Among the 57 patients included in the analysis, 26 (45.6 %) had a history of SARS-CoV-2 infection. Patients with hematologic cancers exhibited lower neutralizing antibody responses compared to those with solid tumors for Omicron subvariants BA.1 (24.44 % vs. 71.68 %, p = 0.020), BA.2 (48.22 % vs. 94.59 %, p = 0.006), and BA.4/5 (24.76 % vs. 78.06 %, p = 0.046). Among uninfected patients (n = 31), sVNT inhibition scores were significantly lower across all subvariants (e.g., 5.89 % for BA.1 vs. 58.11 % in infected, p = 0.0025). Treatment delays due to infection were observed in 9 patients (17.75 days on average). Although no deaths were directly attributed to infection, one patient died due to disease progression following a treatment delay caused by the infection.

CONCLUSIONS

Patients undergoing chemotherapy displayed weak neutralizing responses against Omicron subvariants, especially those with hematologic cancers or no prior infection. Consequently, it is crucial to actively recommend additional vaccinations with bivalent or newly developed vaccines for these vulnerable patients.