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COVID-19, Vaccines, and Cancer: We Don’t Have All The Answers

With all the talk about COVID vaccinations, cancer patients have to be asking what it means for them. And aside from some general reassurances, there is a lot we don’t know about how effective those vaccines will be in patients with cancer. 

What we do know that many are at risk of severe adverse outcomes should they become infected with the virus itself and vaccines are one among several strategies to keep patients with cancer safe from the ravages of COVID and its consequences. 

There are a couple of important points to keep in mind when we talk about patients with cancer and the vaccines currently available in the United States. 

First and foremost, cancer patients are unique individuals. They are unique regarding their age and their sex. They are unique about their underlying “routine” medical conditions such as coronary artery disease, diabetes and hypertension. They are unique when it comes to the type of cancer they have, and they are certainly unique when it comes to their treatments, when they started and when they were completed. In other words, a patient with a small skin cancer removed by straightforward surgery is a lot different than someone with recurrent lymphoma who has received CAR-T treatments. All of those and more are important factors when determining the risk of an adverse outcome from a COVID-19 infection.

Another point to remember is that when the vaccines were tested, patients undergoing active, intense treatment for their cancers were not part of the clinical trials. Vaccine trial participants were mostly healthy, active adults. Immunocompromised patients of all types—that includes other illnesses such as advance rheumatoid arthritis, liver disease, transplants of various organ types and those receiving immunosuppressive drugs for other indications—weren’t part of the trial landscape.

Simply stated: we are just now getting the early reports of vaccine effectiveness in patients with serious, advanced illnesses. And those reports are limited in time and scope, some of them reporting initial observations shortly after the administration of a single dose of a two dose vaccine regimen. 

That information may give us some clues as to immediate or intermediate side effects and some early signals as to how effective the vaccines may be in these patient populations, however they must be considered preliminary in scope. We still have a long way to go to better understand the impact and effectiveness of COVID vaccines in these circumstances.

For example, a paper just published in the Lancet by researchers from Israel makes the observation that one of the vaccines was well tolerated without unusual side effects in patients with cancer receiving immunotherapy drugs. It doesn’t tell us whether or not the vaccine was equally effective at preventing clinical or asymptomatic COVID-related illness when compared to a group of “normal” people and it doesn’t tell us whether the antibody responses were similar or even sufficient. 

Another research letter published recently in JAMA looked at the effectiveness of the mRNA vaccines available in the United States in patients with organ transplants of various types after a single dose of vaccine. However, the reality is that the true impact of these particular vaccines (Moderna and Pfizer) can only be measured several weeks after the second dose and also by determining whether those patients avoid serious illness, hospitalization and death in a manner similar to that seen in the initial large scale clinical trials that led to approval of the vaccine.

436 patients were evaluated in the transplant study, and all were receiving a variety of medications to prevent their bodies from rejecting the transplanted organs. 52% received the Pfizer-BioNTech mRNA vaccine, while 48% had received the Moderna mRNA vaccine. 

At a median of 20 days (median means half were less than 20 days and half were longer than 20 days) after receiving the first dose of the two dose regimens only 17% had evidence of antibodies in their blood. There were differences in antibody levels depending on the type of medicines they were taking to prevent rejection, however more interesting was the observation that transplant patients who received the Moderna vaccine were more likely to have an immune response than those who received the Pfizer vaccine (69% vs 31%). 

It is critical not to draw an absolute conclusion from these data that one vaccine is better than another, since the study was not designed to answer that question. The data is strictly informational, and further studies are required. What is important is the observation that so few of the patients developed a meaningful vaccine response after immunization.

We will eventually see more detailed and more robust studies that can better answer the questions about the effectiveness of the COVID vaccines in cancer patients and others whose immune systems are compromised. Right now it is simply too early to know much that is generalizable to those with serious chronic illnesses, especially those receiving intensive treatments. And we really need to know not only if cancer patients can mount an immune response to the vaccine, but once vaccinated how effective the vaccines are against preventing serious illness, hospitalization and death.

As you follow this discussion, you begin to understand the complexity of the situation. 

Some patients who have received intense immunotherapy with CAR-T—which wipes out antibody-forming B cells—may not have any humoral antibody response to a COVID vaccine (anecdotally, I am aware of one such situation). However we don’t know whether that person may still have protection by the vaccine through activation of the cellular immune system, a sort of “memory” system that can be alerted when our bodies detect an abnormal invader such as a virus or even a single cancer cell. It doesn’t help that in patients with cancer the cellular immune system is already frequently compromised.

We will be hearing a lot more about the effectiveness of these vaccines as more patients with cancer—especially those in active treatment—get the vaccine and are exposed to the virus. However, there are many with cancer and those clinicians and team members who care for those with cancer who want to know what they need to do right now.

The answer from most experts is they should be vaccinated as soon as possible. Less certain is the best time to get vaccinated in terms of one’s treatment schedule. Some say to try to schedule the vaccine in between treatments or just before the following treatment course, but there is no hard and fast rule. We will find out soon enough, however getting the answer to the best timing for vaccination is a question many are facing without good science and evidence to provide the answers they need.

Which brings us to another uncomfortable fact: 

Even if vaccinated, it would appear that patients receiving active cancer therapy, those who have recently completed active therapy, and those with certain types of cancer such as lymphoma and leukemia—and maybe others—should likely continue to follow the COVID precautions we all now know very well. 

In other words, getting vaccinated does not mean you can let your guard down. Stay careful, stay cautious, and stay well. We are not out of the woods just yet, and especially for those with cancer completing a course of vaccine is not a free pass into life as it used to be, for all the reasons outlined above. Until we know more about the effectiveness of the vaccine in you as an individual, until we know whether or not the virus is really under control as a result of community immunity, until we know that the variants can or cannot “penetrate” the protection of the vaccine, it is prudent—even essential—for those with cancer to be cautious. 

Two final thoughts: 

First, as with every vaccination program an its impact on those with cancer, it is not all about you. It is about everyone around you. That means they have to be careful as well, especially as you come in contact with others. It would be prudent for those in your household to be vaccinated as well. It may not be 100% preventive, but it is at least one more element in a comprehensive program of safety. 

And second, your healthcare team is your source of information that is most relevant to you. If you have a question, ask them. If you have a concern, ask them. They may not be able to give you an exact answer since there is so much we still don’t know. But they should be able to know how best to respond to you about your particular situation. 

We can write and talk about the big picture, however ultimately what you need to do to stay safe, and how to stay safe is all about you and no one else. Make certain you are informed, and stay vigilant. That vigilance right now may be one of the most important things you can do on your journey to get to a successful destination. 

3 thoughts on “COVID-19, Vaccines, and Cancer: We Don’t Have All The Answers”

  1. My husband, 4-time BMT cancer patient and still taking immunosuppressant drugs, just had his 2nd Pfizer vaccine. I had mine as well. Doctors advised holding immune-suppressing drugs for a couple of days before the vaccination and then 4-5 days afterwards. The plan is to have an antibody test in a month. Since we aren’t that far out into vaccinating immune-suppressed cancer patients, or even organ transplant patients it will be a while before the data is collected and conclusions can be drawn. Until we learn more, we will be conducting our lives just as cautiously as we have for the past year. Still not within hugging distance!

    1. Thanks for the note. And I agree: caution advised.

      One thing we all have to keep in mind (and I say this based on personal family experience of someone having a COVID-like illness 6 weeks following their second vaccination): the antibody test mentioned is a good idea, however it is “qualitative” not “quantitative”, meaning it is basically “yes/no” re detecting antibodies, which does not tell how much antibody is present. In simpler terms, antibodies could be present but in lower amounts than we would like. That’s why it’s a good idea for cancer survivors and those in active treatment to continue to practice general safety measures following vaccination especially in community settings. That doesn’t mean not seeing family, or traveling safely consistent with CDC guidelines. Just don’t abandon all caution.

      We need the data to get the answers to these questions for those with cancer, and I suspect there are a number of centers working on that as we write this. Time, experience, and research will sort out the answers.

      Be well,


      1. Thanks for the reply Dr. Len! I just caught up with it. We continue to take precautions and do what is reasonable and necessary to do. Hoping for some good data down the road! Till then, the caution flag remains up! Kathleen

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