A COVID-19 booster shot may be beneficial for patients with cancer who are undergoing treatment, according to new findings from an Israeli case-control study.
The seropositivity rate among the patients with cancer remained high (87%) about 4 months after the patients had received the second BNT162b2 (Pfizer/BioNTech) vaccination. However, the median IgG titer in the patients and the control persons who were without cancer decreased over time. Notably, in a previous analysis that the authors conducted and in the current one, the IgG titers were statistically significantly lower in the patients with cancer as compared to control persons.
The correlation between antibody levels following vaccination and clinical protection has yet to be proven, but the accumulating evidence supports antibody response as a possible correlate of disease protection.
“Our data can’t predict if a third booster dose is necessary,” said study author Salomon M. Stemmer, MD, professor at the Institute of Oncology of Rabin Medical Center, Petah Tikva, Israel. “It does seem quite logical that a booster dose will cause an increase in IgG levels.”
The findings were published Aug. 11, 2021, in a research letter in JAMA Oncology.
In their previous study, Dr. Stemmer and colleagues compared the rates of anti–spike antibody response to the initial shot of the BNT162b2 vaccine among 102 adults with solid-tumor cancers who were undergoing treatment with that of 78 healthy control persons. They found that a high percentage of patients undergoing treatment for cancer (90%) achieved a sufficient antibody response to the BNT162b2 vaccine.
Booster endorsed
Responses to COVID-19 vaccination have varied among patients with cancer. For patients with solid tumors, responses have been good even while the patients were receiving systemic therapy. However, among patients with blood cancers, particularly those receiving immunosuppressive therapies, responses have been poor. Studies have identified factors associated with a poor response, but it has been unclear whether to recommend booster shots.
In August the Food and Drug Administration authorized a third dose of either the Pfizer or the Moderna COVID-19 vaccine for all individuals with compromised immune systems. Those eligible for a third dose include solid-organ transplant recipients, those undergoing cancer treatments, and people with autoimmune diseases that suppress their immune systems.
IgG titers lower in cancer patients
In the current analysis, the authors evaluated the anti-S response in the patients with cancer approximately 4 months after they had received the second vaccine dose. They compared the responses in those patients with the responses in a control group.
The cohort included 95 patients from the prior study and 66 control persons. The most common malignancies were gastrointestinal (26%), lung (25%), and breast (18%).
All patients were receiving systemic therapy. Chemotherapy was the most common (28%), followed by immunotherapy (21%) and combination chemotherapy/biological therapy (20%).
At a median of 123 days after the second vaccination, 83 patients with cancer (87%) and all of the control patients (100%) were seropositive for anti-S IgG antibodies. The median titer levels were significantly lower among case patients as compared with control patients (417 AU/mL [interquartile range, 136-895] vs. 1,220 AU/mL [IQR, 588-1,987]; P < .001)
There was a 3.6-fold range in median titer values across tumor types and an even wider range (8.8-fold) across the different types of treatment. The lowest titers were observed among patients who had received immunotherapy plus chemotherapy/biological therapy (median [IQR], 94.4 [49.4-191] AU/mL vs. 147 [62.8-339] AU/mL).
In an exploratory multivariable analysis, treatments with chemotherapy plus immunotherapy and immunotherapy plus biological therapy were significantly associated with lower IgG titers.