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As a Cancer Patient, Will I Need an Extra Dose of a COVID-19 Vaccine?

As a Cancer Patient, Will I Need an Extra Dose of a COVID-19 Vaccine?

Published on August 16, 2021

Researchers Are Studying if Immunocompromised People Need Additional Shot

This is the sixth in a multipart series exploring important questions about COVID-19 and its unique impact on cancer patients. In this series, Patient Power went to the experts to get the facts about COVID-19 and how it affects prevention, screening, treatment, and research.


Update: On Aug. 12, the U.S. Food and Drug Administration expanded the emergency use authorizations for the Pfizer and Moderna COVID-19 vaccines to allow some immunocompromised people to receive a third dose. On Aug. 13, the Centers for Disease Control and Prevention recommended that individuals receive an additional vaccine dose if they are moderately to severely immunocompromised. This group includes people who have been receiving active cancer treatment.


Individuals who are immunocompromised, including people with cancer, are wondering if they will need an additional dose of a COVID-19 vaccine to increase their level of protection against the coronavirus. The Advisory Committee on Immunization Practices (ACIP), which makes recommendations to the Centers for Disease Control and Prevention, met on July 22 to discuss this issue, among other topics. The meeting was a preliminary step in discussing the safety and effectiveness of additional vaccine doses before any new recommendations can be made.

When a person has cancer, there are two main reasons why they have an increased risk of infection: Either the disease itself or its treatment may cause suppression of the immune system. When this happens, a person may be considered immunocompromised. It is estimated that close to 3% of the U.S. population is immunocompromised, including those with solid tumors and blood cancers, people who have had organ or stem cell transplants, and those being treated with drugs that affect the immune system, including certain chemotherapy medications and corticosteroids.

While research indicates a very strong response to the COVID-19 vaccines in the general population, there is growing evidence that some people who are immunocompromised have a less robust immune response, even after they have been fully vaccinated.

Let’s review a bit. With rare exceptions, it is vital for everyone with cancer to get a COVID-19 vaccination as soon as they can, including those on most active treatments. Many experts at the ACIP meeting reemphasized the importance of vaccinations for people who are immunocompromised and further pointed out the key role of a “circle of protection” surrounding those who are immunocompromised consisting of other vaccinated individuals. It is important that all household members and others you are in close contact with are vaccinated.

Should an Additional Vaccine Dose Be Considered Now?

Research is just starting to identify the effectiveness of the standard vaccine approach in immunocompromised individuals. While most people with cancer have at least some immune response following the standard doses of a COVID-19 vaccine, studies show that immunocompromised patients can be less likely to develop antibodies to the coronavirus, which leaves them at a greater risk of serious breakthrough infections following vaccination than those without any preexisting conditions. Early reports have found that those with blood cancers, as well as people who have had organ transplants, may be particularly vulnerable. One strategy to increase protection is to provide an additional dose of the vaccine to those who are immunocompromised.

Patient Power spoke with experts Mounzer Agha, MD, Director of the Mario Lemieux Center for Blood Cancers at UPMC Hillman Cancer Center in Pittsburgh, and Rachna Shroff, MD, Chief of the Section of GI Medical Oncology and Associate Professor of Medicine in the Division of Hematology/Oncology at the University of Arizona Cancer Center in Tucson, about this topic.

Dr. Agha’s study, published as a preprint that has not yet been peer-reviewed, looked at antibody responses to either the Pfizer or Moderna vaccines in people with blood cancers, such as chronic lymphocytic leukemia, lymphomas, and multiple myeloma. Only about half of these patients had an antibody response to the vaccine series overall, and only about 20% of patients with B cell chronic lymphocytic leukemia had detectable antibodies. “That means they are really unprotected,” Dr. Agha explained.

Dr. Agha said it is possible that an additional vaccine may increase the antibody response for many. But when asked if immunocompromised patients should seek out a third vaccine on their own, he explained, “My answer is always that while I can’t tell you what to do, my recommendation is not to get another vaccine now, outside of a clinical trial.” Not all cancer patients are the same, and we don’t know exactly who needs an extra dose and what the best timing should be, he explained. In addition, he pointed out that the issue of safety regarding an extra vaccine dose has not been resolved.

Dr. Shroff offered similar advice. Her team has completed a research project evaluating the antibody response to the Pfizer vaccine in people with solid tumors, such as breast and gastrointestinal cancers, who were on active chemotherapy. The study has not been peer-reviewed and published, but in general, the researchers found that while most patients with cancer had a response to the vaccine (80% had antibodies detected after the second dose), this was not as good as the response in a healthy comparison group, who all had antibody responses to vaccination. She said she believes that a third dose may lead to antibody responses in cancer patients that are similar to the antibody responses of healthy people who are fully vaccinated. They are now in the midst of another study to look at that possibility.

Dr. Shroff agrees that we need to wait a bit longer to get more data before moving forward with any recommendations. “It is so important that we ask these questions and that we ask them systematically… This is complex and we really don’t fully understand what is happening,” she said.

Outstanding Questions

There are many unanswered questions about the advisability of getting additional doses of COVID-19 vaccines, beyond safety and effectiveness. These include how to best choose which vaccine to get and what the ideal timing might be, whether vaccines should be mixed and matched (a Moderna vaccine after a Pfizer series, for example), if people who had a previous COVID-19 infection should be treated differently than those who have never been infected, and how people will be evaluated to determine if an extra dose is warranted.

The hope is that many of these questions will be answered fairly soon. There are research trials beginning to look at these issues. If you are interested in participating in a trial, it is best to talk to your oncologist to see if you may be eligible. Dr. Shroff explained that there are mostly small pilot studies within cancer centers right now, so that is the best way to get involved.

At the ACIP meeting, experts noted that the CDC will not make a recommendation on additional doses until the U.S. Food and Drug Administration (FDA) has taken regulatory action allowing the administration of further doses. However, Amanda Cohn, MD, the CDC’s chief medical officer for vaccine policy, also reported that the agency is actively looking at options to speed up the process of allowing immunocompromised patients to get extra vaccine doses. This may allow clinicians to offer a third dose to those who are immunocompromised before such a strategy is authorized by the FDA or recommended, so stay tuned for developments.

In the meantime, the bottom line is that people with cancer should continue to follow infection prevention measures (masks, handwashing, and crowd avoidance) and “insist that everyone around you is vaccinated,” Dr. Agha said. “If you are going somewhere where unvaccinated people may be present, you must keep your distance, wear a mask, stay outside, or consider not going.”

~Susan Yox, RN, EdD

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