It is currently unclear whether immunity after vaccination lasts as long for cancer patients as it does for healthy individuals, Dr Thakkar said. She and her colleagues are planning to measure antibody levels in the cancer patients from their prior study5 at 4 to 6 months after immunization. 

The study by Ehmsen et al showed that the number of patients with detectable antibodies dropped from 93% at 36 days after immunization to 86% at 3 months after immunization.2

The study by Dr Shroff and colleagues revealed a lag among the solid tumor patients, compared with the healthy control individuals, in the production of SARS-CoV-2-specific memory B cells and T cells.5 

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Unlike the healthy control individuals, cancer patients only generated B cells after the second immunization, and the level of T cells in patients after the second dose was similar to that in the control individuals after the first dose.

This finding indicates “there would be potential for immunity, but it was a delayed takeoff,” Dr Shroff said. As a result, she and her colleagues suggest that an additional dose may “elevate antibody responses in cancer patients” to those seen in healthy individuals after 2 doses. 

Questions Remain

Although studies have shown that patients with solid tumors have better responses to COVID-19 vaccination than do patients with hematologic malignancies, it still isn’t clear if patients with certain types of solid tumors fare worse than others, according to Dr Shroff.

Another unanswered question is whether certain chemotherapy regimens impair response to COVID-19 vaccination more than others.

“Unfortunately, our patient population was too small to really say,” Dr Shroff said. “As we hopefully continue to follow patients prospectively, we can get a better sense of those things because I think it is those nuances that are going to matter.” 

Another question is whether there is optimal timing for COVID-19 vaccination for patients who are receiving anticancer treatment. Although data are lacking, there is guidance that “rationally makes sense,” Dr. Shroff said, such as trying to get patients vaccinated before they start chemotherapy.1 

For those who are already on chemotherapy, she added, it is probably best to vaccinate about 1 week after the start of a cycle, giving patients’ immune cells time to recover.

“In the beginning, oncologists just wanted to get the vaccine to patients because we knew our patients were high risk and something was better than nothing,” Dr Shroff said. 

Now, she and others are trying to time the vaccinations a little more strategically, Dr Shroff said. She recommends that her patients get the additional booster because “there are no safety concerns, and if you didn’t already have a great response, we are hopefully boosting it.” 

Disclosures: Dr Shroff and Dr Thakkar reported having no relevant conflicts of interest.  


1. Corti C, Crimini E, Tarantino P, et al. SARS-CoV-2 vaccines for cancer patients: A call to action. Eur J Cancer. 2021;148:316-327. doi:10.1016/j.ejca.2021.01.04

2. Ehmsen S, Asmussen A, Jeppesen SS, et al. Antibody and T cell immune responses following mRNA COVID-19 vaccination in patients with cancer. Cancer Cell. 2021;39(8):1034-1036. doi: 10.1016/j.ccell.2021.07.016

3. Addeo A, Shah PK, Bordry N, et al. Immunogenicity of SARS-CoV-2 messenger RNA vaccines in patients with cancer. Cancer Cell. 2021; 39(8): 1091-1098. doi:10.1016/j.ccell.2021.06.009

4. Ligumsky H, Safadi E, Etan T, et al. Immunogenicity and safety of the BNT162b2 mRNA COVID-19 vaccine among actively treated cancer patients. J Natl Cancer Inst. Published online August 28, 2021.

5. Thakkar A, Gonzalez-Lugo JD, Goradia N, et al. Seroconversion rates following COVID-19 vaccination among patients with cancer. Cancer Cell. 2021;39(8):1081-1090. doi:10.1016/j.ccell.2021.06.002

6. Shroff RT, Chalasani P, Wei R, et al. Immune responses to COVID-19 mRNA vaccines in patients with solid tumors on active, immunosuppressive cancer therapy. medRxiv. 2021; doi:10.1101/2021.05.13.21257129

7. Coronavirus (COVID-19) update: FDA authorizes additional vaccine dose for certain immunocompromised individuals. News Release. US Food and Drug Administration. Published August 12, 2021.

8. A third dose of the COVID-19 vaccine recommended for some cancer patients with weakened immune systems: Latest information. Memorial Sloan Kettering Cancer Center. Published August 19, 2021. 

This article originally appeared on Cancer Therapy Advisor