Vaccination - yes or no?

Immunity is the state of protection of the body from infectious diseases, and can be acquired through an immune response obtained through immunization, past infection, or other non-immunological factors. Immunity can be acquired actively (exposure to an antigen, for example after a past illness) or passively (providing IgG antibodies to the body). Vaccination is one of the ways to create immunity to a specific infectious agent, and the introduction of vaccination is considered one of the greatest achievements of modern medicine, because it has practically eradicated some previously common and deadly diseases. There are several types of vaccines: live, attenuated vaccines, dead (inactivated) vaccines, toxoid vaccines, and subunit, polysaccharide vaccines. Today, vaccination, under the influence of some supporters of alternative medicine, is attacked as dangerous and harmful to human health, but this has no scientific basis, quite the opposite. But what about vaccinating cancer patients?

Infection in immunocompromised patients (patients with weakened immunity, and this group certainly includes cancer patients) leads to increased morbidity (sickness from other diseases), but also mortality (death), and antimicrobial drugs (antibiotics) are often less effective in such patients. Therefore, prevention of infection in immunocompromised individuals is of utmost importance. Cancer patients are, in accordance with the above, at an increased risk of infection . The risk of infection depends on the type of malignant disease and the type of cancer treatment. When deciding on the type of vaccine, preference is given to the inactive variant. As a rule, the use of vaccines is not recommended during cancer treatment itself. The optimal time for immunization is before the start of chemotherapy and/or radiotherapy treatment, and if it is an inactive vaccine, at least 2 weeks before chemotherapy, and if it is a live vaccine, at least 4 weeks. In the event that vaccination is nevertheless indicated during treatment, the use of live, attenuated vaccines is not recommended, and indeed should be avoided. Namely, even such weakened vaccines carry risks and can lead to infection in people with weaker immunity. As for the dead vaccine, it is not recommended either, because such vaccination can be ineffective and give the patient a false sense of security.

When it comes to widespread influenza vaccination , which is of most interest to oncology patients, there are many guidelines and all agree that oncology patients should be vaccinated once a year. The response to the influenza vaccine may be best if it is administered between chemotherapy cycles, i.e. at least 7 days after the last administration or at least 2 weeks before the administration of chemotherapy/immunosuppressive therapy, with an inactivated virus given the theoretical risk of developing infection in immunosuppressed patients with a live attenuated virus. Also, all household members should be vaccinated against influenza virus (with any type of vaccine). Administration of the vaccine on the same day as chemotherapy is not recommended. In case of exposure to the influenza virus, patients with neutropenia (decrease in blood counts due to oncology therapy) should receive post-exposure antiviral prophylaxis for 5 days, regardless of whether they have been vaccinated. For more details, we definitely recommend contacting the competent family doctor who is responsible for administering the vaccine and who will be able to choose the best type of vaccine for the patient in accordance with the relevant recommendations.

Image 1. Most experts believe that cancer patients should get vaccinated against the flu once a year. Contact your family doctor to schedule an appointment!

Should and can oncology patients be vaccinated against COVID-19? These days, oncology patients are frequently asking their doctors whether they can and should be vaccinated against the coronavirus, how the vaccine will affect oncology treatment, and whether there are differences between vaccines. What does the data we have so far tell us? Let's start in order.

It should be emphasized that compared to the rest of the healthy population, oncology patients have a higher risk of contracting a severe form of the disease, COVID-19. At the same time, the risk of death in case of infection according to the available data of the analysis of 17 studies conducted in the first wave of the epidemic was estimated at around 25%. Subsequent, more complete data nevertheless speak of a lower mortality rate, which is still significantly higher than in the healthy population. Patients with hematological malignancies (for example, leukemia) are at the highest risk. Additionally, the risk is higher for men (1.16x higher risk), older than 65 years (1.27x) and with comorbidities (1.12x). Overall, the risk of a severe form of the disease of COVID-19 in oncology patients is almost three times (2.73 times) higher compared to the healthy population.

Furthermore, when we talk about oncology patients, it is known that they initially have a weakened immune system, which is often further impaired by intensive oncology treatment, such as chemotherapy. If we know that the development of antibodies to a disease after vaccination requires activation of the immune system, the question arises whether oncology patients who are immunocompromised (with a weakened immune system) can develop an immune response after vaccination or will the vaccine be poorly effective? Of course, we do not yet have a definitive answer to this question, primarily because the diagnosis of cancer was the exclusion criterion in more or less all clinical studies that analyzed the efficacy/safety of the coronavirus vaccine. However, we are guided by previous data and experience with other vaccines, most often those against influenza. Namely, it has been proven in several clinical studies that vaccination against influenza also induces a satisfactory immune response in immunocompromised patients, i.e. the vaccine creates protection against the disease despite weakened immunity. Analogously, the same is expected with vaccination against COVID-19. According to the VACANCE study, the development of immunity occurred regardless of the type of oncology therapy and treatment protocol (2-week, 3-week, continuous therapy, etc.).

Regarding the type of vaccine, two main categories of vaccines are currently available. It is important to emphasize that these vaccines do not contain the entire virus, but only the genetic message for a single viral protein within a lipid nanoparticle (mRNA-based vaccines: Pfizer, Moderna) or packaged within a harmless adenoviral vector (AstraZeneca/Oxford, Johnson&Johnson). Therefore, both types are considered safe for oncology patients, and the world's major oncology societies agree that oncology patients should be vaccinated with one of the currently available vaccines. Vaccination with inactivated or live vaccines is not recommended. When deciding who and when to vaccinate, given the limited data available, the benefits and potential risks should always be weighed, including the risk of infection and development of a severe form of COVID-19. Some of the priority groups for vaccination according to available data are: older oncology patients (especially those aged 74 years and older), hematology patients, those requiring active oncology treatment (e.g. chemotherapy), patients with metastatic disease and comorbidities.

Vaccination is safe and reliable in patients who are currently undergoing follow-up, however, the question arises of how to vaccinate patients who are undergoing oncological treatment. For now, we do not have specific recommendations on when exactly to vaccinate patients who are currently undergoing therapy, but the general recommendation is to try not to interrupt or delay the application of oncological treatment in order to carry out vaccination. Of course, the aggressiveness of the malignant disease should be assessed on the one hand and the risk of contracting COVID-19 on the other. Some of the advice is to administer vaccination if possible before the start of active oncological treatment (>2 weeks) or after its completion. If this is not possible, vaccination can also be performed between 2 cycles of therapy, avoiding the so-called nadir (the time when blood tests are at their lowest point as a result of the treatment applied). For example, for three-week protocols, vaccination is recommended in the 3rd week of therapy (just before the start of a new cycle). It is important to avoid the application of oncological therapy during the period when side effects of vaccination are expected (2-3 days after vaccination; more pronounced after the second dose; more common in younger people), as well as within 2 weeks before major surgical procedures.

When it comes to oncological treatment and vaccination, the biggest concerns are with the use of immunotherapy, since it modulates the activity of the immune system. Namely, the response to COVID-19 disease (activation of the myeloid lineage) can be compromised by interrupting the so-called PD-(L)1 signaling pathway, which is affected by many of the drugs used in immunotherapy. Also, viral infections (including COVID-19) can lead to increased expression of PD-L1 on white blood cells (T lymphocytes) and other infected tissues, which can lead to additional and significant damage in combination with immunotherapy. For this reason, some European centers have issued recommendations for deviations from standard protocols, such as a pause in treatment in selected patients with metastatic melanoma in whom vaccination is planned, who are treated with immunotherapy and have long-term stable disease. Despite this justified caution, studies conducted so far have shown that vaccination (against influenza) is effective even during immunotherapy and without significant side effects for most patients.

In conclusion, vaccination is recommended for oncology patients, regardless of other indications. It is important to identify those most at risk, such as hematology patients, older oncology patients, those with advanced disease... Although there are no obvious reasons to worry about vaccine safety, it is necessary to closely monitor and supervise oncology patients after receiving the COVID-19 vaccine in order to assess possible complications and measure clinical outcomes. It is also important to encourage vaccination of close contacts of oncology patients and, after discussing the patient and assessing the overall risk, make a joint decision on vaccination!

Additional interesting facts

If you are interested in more about types of immunity and types of vaccines in general, we recommend the scientific paper: Baxter, D. (2007). Active and passive immunity, vaccine types, excipients and licensing. Occupational Medicine, 57(8), 552–556. doi:10.1093/occmed/kqm110.

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