Pfizer COVID-19 Vaccine Deemed Safe for Patients Undergoing Cancer Treatment Despite “Lagging” Immune Response in Some Malignancies


Despite some delayed immune responses, the Pfizer COVID-19 vaccine appears safe and effective in patients with cancer who are receiving treatment for their disease.

The Pfizer COVID-19 vaccine appears to produce a safe and effective immune response in patients with certain cancer types who are undergoing active treatment, although notably some patients with solid malignancies may have delayed immune responses, according to a press release.1

The study compared patients who were undergoing treatment for cancer with non-cancer controls and found a lagging immune response time in some solid tumors, such as colon, breast, and lung cancer. Investigators only focused on the Pfizer 2 dose vaccine and not Moderna, which has a similar composition; investigators are unsure whether it would yield the same response.

“Patients with solid tumors do develop antibodies to the vaccine, but this process is lagging compared with the general population, and one dose is not enough,” study co-author Irit Ben-Aharon, MD, PhD, of the Israel Cancer Research Fund said in the press release.

Investigators caution that patients undergoing treatment with chemotherapy and radiotherapy should be monitored after receiving the vaccines, as it may potentially cause changes in certain liver enzymes.

This study focused on 232 adult patients undergoing cancer treatment and 220 healthy adults. Following administration of the first dose, patients with cancer had 29% detectable antibodies in the bloodstream compared with 84% in healthy adults.

When patients with cancer received the second dose, the antibodies rose to 86%. Investigators are still monitoring these patients for 6 months to see if their immune response declines or if a booster shot will be needed.

“Based on their findings, however, people undergoing cancer treatment can—and should—receive both doses of the vaccine,” Ben-Aharon continued in the press release.

This study, which began in January 2021 and concluded in March 2021, took place in Israel with randomly enrolled patients who had not previously been infected with the COVID-19 virus. The first dataset was taken more than 10 following the first dose of the vaccine, and the second was collected approximately 14 days after the second dose.2

The cohort of patients receiving cancer treatment was comprised of 172 patients (74%) who had metastatic disease. The most common cancer types included gastrointestinal (27%; n = 63), genitourinary (21%; n = 48), lung (19%; n = 45), and breast cancer (18%; n = 42).

Among patients who were 60 years or older, 30% (n= 26) had positive serologic test results compared with 80% (n= 146) in the control group (P< .001). Seropositive patients had a media titer score of 40.25 compared to the control groups 43.5.

In patients who were 60 years or younger, 27% (n= 7) had positive serologic results (median, 72.5) compared with 94% (n= 94) the control group (median, 74.0). There was no difference when investigators looked at age, sex, or disease stage.

Investigators reported an increase in enzymes by 1.5 times in 24 patients for 6 weeks after the first dose. Patients also reported local reaction (69%), with injection-site warmness (9%), redness (8%), and swelling (4%). The most common adverse effects reported included fatigue (24%), muscle and joint pain (13%), and headache (10%). Only 1% of patients reported a fever.

“This cohort study provides data on use of the SARS-CoV-2 BNT162b2 vaccine in patients with solid tumors who are receiving active anticancer treatments in the real-world setting. Although the immunogenicity pattern was gradual and slower than in the noncancer population, after the second dose most patients were seropositive and no documented cases of COVID-19 infection were determined,” investigators of the study concluded.


1. Pfizer COVID-19 vaccine safe, effective in cancer patients, despite 'lagging' response. News release. UPI. July 8, 2021. Accessed July 9, 2021.

2. Goshen-Lago T, Waldhorn I, Holland R, et al. Serologic status and toxic effects of the SARS-CoV-2 BNT162b2 vaccine in patients undergoing treatment for cancer. Published online ahead of print: July 8, 2021. JAMA Oncol. 2021. doi:10.1001/jamaoncol.2021.2675

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