Vaccines and treatment

01Short answer

02Simple explanation

A vaccine shows the immune system a “portrait” of a germ. The immune system studies this portrait and remembers it. Then, when it meets the real germ, it responds faster and more strongly. This matters especially for protection against serious infections.

In some vaccines the germ is killed, or only part of it is present. These vaccines cannot cause disease, so they are usually safe in leukemia too. But because treatment weakens the immune system, they may not give protection as strong as in a healthy person.

In other vaccines the germ is alive but weakened. In a healthy person it causes no illness, but in someone with very weak immunity it can. That is why live vaccines are not given during intensive treatment and for some time afterwards.

Timing is very important. The best response comes before treatment starts. During treatment, doctors may plan a vaccine for days when blood counts are better. After some medicines (for example those that lower B cells), vaccines work poorly for months.

You are protected not only by your own vaccinations but also by those of the people around you. If family members get their flu and other vaccines on time, they are less likely to bring infection home. This creates a protective circle around you.

03Scientific explanation

Live and non-live vaccines: non-live vaccines (the inactivated flu jab, conjugate and polysaccharide pneumococcal vaccines, mRNA and protein COVID-19 vaccines, the recombinant shingles vaccine, hepatitis B, Tdap/Td, HPV and others) can be given to people with weak immunity. Live attenuated vaccines (MMR, chickenpox, yellow fever, live shingles vaccine, nasal flu, oral polio, BCG, oral typhoid, rotavirus) are, according to the 2013 IDSA guideline, usually considered no sooner than three months after chemotherapy ends, and later after anti-B-cell antibodies (for example rituximab) — usually at least six months — and only with the doctor’s agreement.

Key principles of the ASCO 2024 and ECIL 7 guidelines: vaccines should be given before treatment where possible (non-live vaccines ideally at least two weeks before); a seasonal flu jab is recommended every year; COVID-19 vaccination according to current recommendations; a conjugate vaccine against pneumococcal infection; and, in some blood cancers, the recombinant (non-live) shingles vaccine. In people receiving anti-CD20 treatment, the antibody response is usually weak for six months or more after treatment, and this is taken into account when planning vaccines.

After a transplant or CAR-T therapy, protection from earlier vaccines is often lost and the person is re-vaccinated “from scratch”. Under international guidance, non-live vaccines usually start about 3–6 months after a transplant; live vaccines are considered no sooner than two years afterwards, and only without active graft-versus-host disease or immunosuppressive treatment. The exact schedule depends on the centre and on immune recovery.

For family members and close contacts (IDSA 2013, ASCO 2024): they should receive the inactivated flu vaccine, COVID-19 and other age-appropriate vaccines. They can usually also receive live vaccines such as MMR, chickenpox and rotavirus: if a rash appears after chickenpox vaccination, direct contact is avoided until the rash has gone; after changing the nappy of a baby given the rotavirus vaccine, careful hand washing is advised for about four weeks. Oral polio vaccine should not be given to close contacts. The nasal flu vaccine is restricted only for contact with severely immunocompromised patients in a protected environment.

04What happens in the body?

When should you seek urgent help?

Mild soreness, tiredness and a short-lived fever can follow a vaccine. But during treatment call your team straight away if: your temperature is 38 °C or higher — it must be assessed as a possible infection rather than put down to the vaccine; you develop breathlessness, swelling of the face or tongue, or a widespread rash (an allergic reaction — call emergency services); you have been in contact with someone who has chickenpox, shingles or measles — in some cases protective treatment needs to start in time.

Which vaccines are usually recommended?

A seasonal flu vaccine every year (as a jab, not a nasal spray); a COVID-19 vaccine — according to current recommendations; a pneumococcal vaccine; and for some people the recombinant shingles vaccine, hepatitis B, tetanus-diphtheria-pertussis and others. The list is made individually according to age, type of leukemia, treatment and previous vaccinations.

Live vaccines: why caution is needed

In live vaccines the germ is weakened but alive. When immunity is very weak, this germ can cause disease. That is why vaccines such as measles-mumps-rubella, chickenpox, yellow fever, nasal flu and BCG are not given during intensive treatment and for some time afterwards. If you are planning to travel, discuss it with your team in advance: vaccines required for some countries are live.

Timing of vaccines

The best response comes before treatment — where possible, non-live vaccines are given at least two weeks before it starts. During treatment, vaccines are often planned between courses, when blood counts are relatively better. After medicines that lower B cells, vaccines work poorly for months, and sometimes a repeat dose is needed later. It is important not to miss the flu season.

Vaccines for family and close contacts

Household members should have a flu vaccine every year, COVID-19 vaccination and other age-appropriate vaccines. They can usually have childhood vaccines too, including MMR and chickenpox. If a rash appears after chickenpox vaccination, keep your distance until it has gone. If possible, someone else should change the nappy of a baby given the rotavirus vaccine, and hands must be washed carefully.

Questions you can ask your doctor

Which vaccines should I have before treatment starts? When is the best time for my flu and COVID-19 vaccines? Which vaccines must I avoid, and until when? Which vaccines do my family members need? What will my vaccination schedule look like after a transplant or CAR-T therapy? Which travel vaccines could be a problem? Should my antibody levels be checked?

07Key terms

Vaccine

A product that “introduces” a germ to the immune system and creates memory.

Live attenuated vaccine

A vaccine containing a weakened but live germ.

Non-live vaccine

A vaccine containing a killed germ, part of it, mRNA or a protein; it cannot cause disease.

Immune response

The making of antibodies and cell defences against a vaccine or germ.

Re-vaccination

Giving vaccines again from the start after a transplant or CAR-T therapy.

Anti-CD20 antibodies

Medicines that lower B cells (for example rituximab); they weaken the effect of vaccines.

Community protection

Protection of a vulnerable person because the people around them are vaccinated.

Shingles

A painful rash caused by reactivation of the chickenpox virus.

Pneumococcus

A bacterium that can cause pneumonia and meningitis.

Passive immunisation

Short-term protection by giving ready-made antibodies (immunoglobulin).

08Key points

• Vaccines help protect against serious infections in leukemia.
• Non-live vaccines are usually safe.
• Live vaccines are not given during treatment.
• The best response comes before treatment starts.
• A yearly flu vaccine — as a jab.
• Your family’s vaccines protect you too.
• Re-vaccination is needed after a transplant or CAR-T therapy.
• Your hematology team decides your vaccination plan.

09Frequently asked questions

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

1. 1

   Which vaccines can I have during treatment, and which not?

2. 2

   When can I have the flu vaccine?

3. 3

   Which vaccines should my family members have?

4. 4

   When should vaccines be repeated after treatment or a transplant?

My questions

11What to read next

• Immunity and infection preventionHow does the immune system work?
• Immunity and infection preventionVisitors and public places
• Treatment and the treatment processImmunotherapy and CAR-T
• Immunity and infection preventionMonocytes and macrophages
• Treatment and the treatment processStem cell transplant

12Sources

1. Journal of Clinical Oncology (ASCO), 2024. Vaccination of Adults With Cancer: ASCO Guideline
2. Clinical Infectious Diseases (IDSA), 2014. 2013 IDSA Clinical Practice Guideline for Vaccination of the Immunocompromised Host
3. The Lancet Infectious Diseases (ECIL 7), 2019. Vaccination of patients with haematological malignancies who did not have transplantations: guidelines from the 2017 European Conference on Infections in Leukaemia (ECIL 7)
4. Biology of Blood and Marrow Transplantation, 2009. Guidelines for Preventing Infectious Complications among Hematopoietic Cell Transplantation Recipients: A Global Perspective
5. Centers for Disease Control and Prevention (CDC). Altered Immunocompetence — General Best Practice Guidelines for Immunization
6. Centers for Disease Control and Prevention (CDC). Flu and Cancer
7. American Cancer Society. Vaccinations During Cancer Treatment
8. UK Health Security Agency (Green Book). Immunisation of individuals with underlying medical conditions: the green book, chapter 7
9. UK Health Security Agency (Green Book). Contraindications and special considerations: the green book, chapter 6
10. NHS. Vaccinations
11. Centers for Disease Control and Prevention (CDC). Information for Patients Who Are Getting Chemotherapy
12. Blood Cancer UK. Preventing infection