The panel included three in-house specialists: immunologist Thiago Carvalho and oncologists Fátima Cardoso, head of the Breast Unit at the Champalimaud Clinical Centre, and Cristina João, a haematologist in the Haemato-Oncology Unit who also heads the Myeloma and Lymphoma Research Lab at Champalimaud Research.
The webinar started with a presentation by Thiago Carvalho about the virus and the various vaccines against SARS-CoV-2. Then, the communication channel with the public – several hundred participants – was opened to receive questions. Based on the concerns expressed by the public and by the panelists themselves, we elaborated the following list of questions and answers that address some of the most common worries of cancer patients, and which hopefully will inform their decisions as they face the COVID-19 pandemic.
May cancer patients be vaccinated against COVID-19?
They may and they should. Both oncologists agree in saying that recently diagnosed cancer patients and patients already receiving treatment should be included in the priority vaccination groups, because were they to be infected by the SARS-CoV-2 virus, they would have a higher risk than the general population of developing a severe and potentially lethal for of COVID-19.
The Portuguese National Health Service does not include cancer patients in the priority group for vaccination. Should it?
“Cancer patients in active treatment (chemotherapy, radiotherapy, surgery) should, in my opinion, have been included in Phase 1 of the vaccination plan,” states Fátima Cardoso. On the other hand, patients that are already in follow-up or maintenance oncologic treatment should, in her opinion, be included in Phase 2 of the Portuguese vaccination plan.
If you had cancer in the past, do you also have an augmented risk of complications and mortality for COVID-19?
No. People who had cancer years ago and survived the disease should be classed according to other relevant criteria (and not their past cancer).
Wouldn’t it be more prudent to first vaccinate people whose immune systems are strongest, in order to generate herd immunity, which would then protect cancer patients in active or maintenance treatment, whose immune system is weaker?
“If I could erase one phrase from the public consciousness, it would be ‘herd immunity’,” says Thiago Carvalho. ”It’s a fascinating and complex topic, which makes it great for a research project, and terrible as an approach to public policy. It also is mistaken for an end-state. As we see now with the emergence of new variants, viruses and human populations are engaged in an elaborate game of cat and mouse. Vaccines are a better mouse-trap, but it doesn’t mean we should just leave cheese lying all over the floor.” At the moment, we don’t even have data to be sure that people do not still harbour the virus in spite of being vaccinated themselves. Therefore, we don’t know whether they are still capable of infecting unvaccinated people – and this answer may very well vary from vaccine to vaccine.
Are RNA vaccines really safe?
We have no indications of serious causes for concern. There are several types of vaccines. Some, which contain the disease-causing virus in an attenuated or inactive form, have been in use for more than a century. Others are “adenoviral vector” vaccines, in which the vaccinating ingredient is transported to the body’s cells by a “shell” of adenovirus (common cold virus) unable to cause any disease and functioning as a mere “vehicle” for the element that will elicit the response of the immune system to the virus the vaccine is supposed to fight. This is the case of some of the vaccines against the Ebola virus. And lastly, we have RNA vaccines, which, as Thiago Carvalho noted, are those that have raised the most concerns in the public because they are the most recently developed and that there is not enough data about them.
As Thiago Carvalho explained, contrary to what people think, the RNA vaccine technology, which was initially specifically developed to fight cancer by many companies, is already more than a decade old. “This type of vaccine has already gone through several clinical trials and never had safety problems,” he says. Rather, the technique has so far shown poor efficacy against cancer, but continues to be investigated by a few companies for vaccines against several different types of diseases.
It was the SARS-CoV-2 pandemic that revealed the high efficacy of these vaccines against this virus. And the knowledge that had been accumulated over the years was one of the reasons why the development of RNA vaccines against COVID-19 happened in record time. In particular, years of pre-clinical testing were not needed, since they had already been performed with other coronaviruses starting in 2003, at the time of the SARS-CoV-1 (ex-SARS) epidemic that took place in Asia, and later for the MERS coronavirus outbreak. So, in March 2020, combined Phase 1 and 2 clinical trials for SARS-CoV-2 RNA vaccines were able to start immediately, involving hundreds of volunteers. It is very important to note that no stages of the required safety testing in humans were skipped.
But what really accelerated the whole process was something else altogether. “I remember being convinced at the time that it would be impossible to have a vaccine ready at the end of 2020,” said Thiago Carvalho. “If we were able to obtain such clear results in so few months, it was because the pandemic raged out of control in the West.” The spread of the virus in the US, Brazil, the UK, etc., was so fast that we rapidly managed to see, when the different vaccines were tested in tens of thousands of volunteers, that they were highly efficacious in protecting against the virus. In China and other countries that had managed to control the transmission of the virus in the population, this would have taken years to achieve precisely because there wasn’t enough transmission. “That was our contribution: the loss of control over the pandemic in our countries…”, ironized Thiago Carvalho. At the same time, safety data continued to be collected and has not shown any unexpected safety risks.
What is the best type of vaccine for cancer patients?
In Portugal, the Vaccination Plan only includes, at the moment, two types of vaccines: RNA vaccines (Pfizer and Moderna) and adenoviral vector vaccines (AstraZeneca). Their efficacy and safety are similar, although there remain some doubts about the “age limit” for getting the AstraZeneca vaccine.
The determinant factor for choice is the availability of each type of vaccine, said Thiago Carvalho. In Portugal, there are no recommendations and there is no choice.
When a patient receiving or about to receive cancer treatment becomes infected with the virus, is it necessary to interrupt or postpone the treatment?
“Not always,” says Cristina João. “The decision has to be made, in each case, based on the COVID-19 symptomatology and the type of cancer treatment.” For instance, there are treatments that stimulate the immune system and do not interfere with the vaccine against SARS-CoV-2. On the other hand, with chemotherapies that are highly immunosuppressive, it is advisable to stop the treatment until the viral infection has ended, so as to give the immune system the best chances of fighting the infection.
Why do antibodies against the COVID-19 virus run out after vaccination?
They don’t. A small stock remains “stored” inside the cells of the immune system once the acute immunisation phase is finished, ready to mount a defense in case the virus attacks again.
What happens to the viral RNA that was injected into the body at vaccination?
After being used by immune cells to produce the “spike” protein of the virus, which will trigger the immune response, the viral RNA is destroyed by the cellular machinery of the vaccinated individual.
Should cancer treatment be interrupted in order to take the vaccine?
Not necessarily. There are international recommendations about when to vaccinate patients who are in the active treatment phase. If the patient is receiving chemotherapy, the vaccine will not adequately stimulate the immune system against the virus. In this case, it may be advisable to wait ten days and to vaccinate in between two chemotherapy cycles. “But this is a decision that has to be taken on a case-by-case basis”, stresses Cristina João.
For breast and prostate cancer, the hormonal treatments used do not affect vaccination, adds Fátima Cardoso – and therefore do not need to be interrupted. The same goes for immunotherapy, which stimulates the immune system when not used in combination with chemotherapy. Radiotherapy can also be managed together with vaccination.
To summarise, it is essential to determine the best timing for vaccination, but this does not invalidate the need to vaccinate cancer patients, both doctors stress once more.
How is the success of the vaccination ensured in immunosuppressed patients?
“We don’t always know if the vaccine will be effective and whether cancer patients will be able to generate immunity”, said Cristina João. But they should get vaccinated, she insisted.
Is it the oncologist who requests vaccination for his/her patients?
No. This is a process centralised at the national level. But it is the oncologist who has to decide, in each case, whether or not to interrupt chemotherapy. It is important to stress here that, even in cases where the oncologist decides that the chemotherapy should not be interrupted – and the immune response to the vaccine may thus be weaker – the vaccine may still be able to prevent the patient from contracting the most severe and potentially lethal forms of COVID-19.
Are there situations in which a cancer patient should not be vaccinated?
Yes. People with severe allergies to ingredients of the vaccine are excluded from being vaccinated, whether they have cancer or not.
Should patients with auto-immune diseases be vaccinated?
For certain severe auto-immune diseases, vaccination may not be the best strategy. But this must be discussed between the patient and the doctor who oversees the auto-immune disease.
Should patients with leukopenia be vaccinated?
There are different types of leukopenia and not all of them imply that the cancer patient’s leukocyte count is zero, says Cristina João. For patients with resistant leukopenia or lymphopenia, the best moment should be chosen in order to ensure that the immune system will be challenged by the vaccine.
Should a person who does not react well to the flu vaccine be vaccinated against COVID-19?
Vaccination against COVID-19 can cause, just like vaccination against the flu, a series of generally light symptoms, such as pain at the site of inoculation, fatigue, headaches, muscular pain, shivers, joint pain and fever.
What are the side-effects that can arise during the 30 minutes following vaccination? Can they be treated immediately on-site, or could they require hospitalisation?
The most severe side-effect, which is rare, is allergic shock to the vaccine, also known as anaphylactic shock. This is the main reason why people are asked to remain at the vaccination centre for 30 minutes after being vaccinated. Anaphylactic shock is rapidly and safely controlled with medication that is available at the vaccination centre and administered on-site by the health personnel.
Should cancer screening be postponed?
Absolutely not, says Fátima Cardoso. Screening for breast and colorectal cancer were suspended during the first wave of the pandemic, and in 2020, the number of early cancer diagnosis exams performed in Portugal fell by 40%. “This activity has now resumed, but the process is slower,” added Thiago Carvalho.
“We are going to pay a heavy price for this in the coming years,” noted Fátima Cardoso – when many cancers in more advanced stages start to appear because they were diagnosed later.
Because of this, Fátima Cardoso begged people not to continue postponing mammograms and colonoscopies. “Early diagnosis is crucial,” she said. “We are starting to see some availability for these exams at the Health Centres. Do not be afraid to do screenings because of COVID-19. “And if you do not get an answer to your request for an exam the first time around, do not give up. Keep trying.”
By Ana Gerschenfeld, Science Writer of the Champalimaud Foundation.
