mRNA COVID-19 vaccine in patients on cancer treatment: Is response durable?

Christina Lau
12 Aug 2021

Anti-spike (anti-S) immunoglobulin G (IgG) antibody seropositivity rate in patients on active anticancer treatment remains high approximately 4 months after the second dose of the BNT162b2 mRNA coronavirus disease 2019 (COVID-19) vaccine, although median IgG titres are significantly lower than those in healthy individuals, a recent study has shown.

In the prospective cohort study, researchers evaluated anti-S response to BNT162b2 in patients with solid tumours on active anticancer treatment vs healthy controls. Initial findings, after a median of approximately 5.5 weeks from the second vaccine dose, showed seropositivity in 90 percent of patients with cancer (n=90/102) and all healthy controls (n=78/78), while median IgG titre was 1,931 AU/mL vs 7,160 AU/mL (p<0.001). [JAMA Oncol 2021;doi:10/1001/jamaoncol.2021.2155]

Updated results, from 95 of 102 patients with cancer (5 died, 2 withdrew) and 66 of 78 health controls (12 withdrew), showed anti-S IgG antibodies in 87 percent of the cancer patients and all healthy controls after a median of 123 days from the second vaccine dose. Median IgG titres were 417 AU/mL in the cancer patients vs 1,220 AU/mL in the control group (p<0.001). [JAMA Oncol 2021;doi:10.1001/jamaoncol.2021.4390]

The results also showed a 3.6-fold range in median IgG tire values across tumour types and a 8.8-fold range across treatment types, with the lowest titres observed with immunotherapy plus chemotherapy (median, 94.4 AU/mL) or immunotherapy plus biological therapy (median, 147 AU/mL).

An exploratory multivariable analysis showed that treatment with immunotherapy plus chemotherapy or immunotherapy plus biological therapy was the only variable significantly associated with lower IgG titres.

Of the 12 seronegative patients, 8 were seronegative in the previous analysis. One patient with breast cancer who was seronegative in the previous analysis became seropositive in the current analysis, after discontinuation of active therapy.

“Data on the durability of protection after vaccination are limited for healthy individuals and lacking for oncological patients,” the researchers noted. “Our results that seropositivity rate remained high among cancer patients approximately 4 months after the second dose of BNT162b2, while median IgG titres in both groups decreased over time and were significantly lower in cancer patients vs controls.”

However, they also acknowledged the lack of cellular immunity testing and/or neutralizing antibody testing as limitations of the study.

“Although the correlation between antibody levels after vaccination and clinical protection is yet to be proven, the accumulating evidence supports antibody response as a potential correlate of disease protection,” they added. [JAMA Intern Med 2021;181:672-679] “Long-term cellular memory could call into question the need for a third BNT162b2 booster dose.”