Timing a flu shot when you are having chemotherapy

This page is for people having chemotherapy or radiation who want to know when to get a flu shot. It explains what CDC does and does not say, and when to call your team.

Many people arrive at this question having heard something specific. Get it mid-cycle. Get it just before the next dose. Wait until counts recover. Those rules of thumb travel widely.

CDC's page on flu and cancer holds none of them. It gives no timing guidance for flu vaccination relative to chemotherapy or radiation schedules. This page will not fill that silence with a made-up number. It will show you what CDC does say. Then it will send you to the one person who can answer for you: your oncologist.

Flu matters more when you have cancer. CDC says people who have cancer now are at increased risk of serious flu complications. So are people who have had certain cancers in the past, such as lymphoma or leukemia.

Flu shots are safe here. CDC states that flu shots have a long, established safety record. They are safe for people with cancer. CDC recommends injectable flu vaccine for cancer patients.

Earlier is better where possible. CDC's general immunization guidance advises giving all indicated vaccines before chemotherapy begins, when feasible. The same applies before other immunosuppressive drugs, and before radiation or splenectomy. A splenectomy is surgery to remove the spleen.

Protection may be weaker during treatment — but flu vaccine is the stated exception. The same guidance says that vaccination during chemotherapy or radiation should be avoided if possible, except for inactivated influenza vaccine. The reason given is that antibody response might be suboptimal. That exception matters here. The inactivated flu shot is the one vaccine CDC does not tell clinicians to hold back during treatment.

For other vaccines, one given within 14 days before starting immunosuppressive therapy, or while it is being given, may not count. The person may be considered unimmunised and need revaccinating at least three months after therapy stops, once immune competence has returned.

Everyone around you counts. CDC states that it is important for people who live with or care for cancer patients to be vaccinated against seasonal flu.

Chemotherapy cycles are not all alike. White cells dip at different points. They stay down for different lengths of time. Recovery differs too. It depends on the regimen and on you.

Your oncologist knows that pattern. Ask when to have your flu vaccine and you are asking them to place it sensibly in a schedule they already understand. It is a question they field every fall.

Ask for a date rather than a principle. A date can go on a calendar.

CDC gives specific advice here, and it is easy to miss. Ask your doctor whether you should have flu antiviral drugs if you have been in contact with someone known or thought to have flu, and either of these is true:

• You have received cancer treatment such as chemotherapy or radiation therapy within the last month.
• You have a blood or lymphatic form of cancer.

Make that call promptly. Do not wait for symptoms to appear.

CDC notes that a fever can be a sign that a person with cancer has flu or another illness. It says patients experiencing fever should contact their doctor immediately.

CDC's guidance for people in cancer treatment gives the temperature figure most cancer teams use: a fever of 100.4 °F (38 °C) or higher. (NCI prints the same 38 °C threshold as 100.5 °F.) NCI also warns against taking medicine to bring a fever down before you speak to your doctor. Doing so can mask a serious problem.

So get vaccinated on a date your team chooses. Get your household vaccinated too. And treat any fever as a reason to ring, not a reason to wait until morning.