Vaccination protects people with cancer well against COVID disease, even when it is caused by a virus variant.

This is the conclusion of an international team led by haematologist Marie von Lilienfeld-Toal.

The researchers systematically re-evaluated dozens of studies and concluded that vaccination, especially repeated vaccination, effectively protects cancer patients against COVID infection.

The results of the literature search were published in Nature Reviews Clinical Oncology.

Infection with SARS-CoV-2 is particularly dangerous for people with cancer. "The lethality is about twenty percent in this group," says Marie von Lilienfeld-Toal.

The internist and haematologist is a professor at the Department of Internal Medicine II at Jena University Hospital, and her research group "Infections in Hematology/Oncology" conducts research at the Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (Leibniz-HKI) in Jena, Germany. As vice-chair of the Infections in Hematology and Oncology Working Group of the German Society for Hematology and Oncology (DGHO), she has been involved in the development of numerous guidelines for the treatment of COVID in cancer patients since the beginning of the pandemic.

"Back in early 2021, we already made recommendations on COVID vaccination in cancer patients," von Lilienfeld-Toal notes. Now, she and an international research team have re-evaluated more than 60 studies on the immune response in cancer patients to give a comprehensive analysis of the efficacy and potential risks of vaccination in this group.

Her conclusion: "It can be assumed that vaccination is indeed effective in cancer patients."

This group of people does not participate in registration studies, which means that the efficacy and risks specific for this cohort can only be retrospectively evaluated.

"Our review has shown that the efficacy of the vaccination is around 80 percent. This is very good even compared to the flu vaccination, where the effectiveness is generally much lower," she explains.

The mRNA vaccines were found to be the most effective. The analysis also includes an assessment of vaccine efficacy against the new omicron variant of SARS-CoV-2.

According to von Lilienfeld-Toal, multi-dose COVID vaccine series are helpful for cancer patients.

"We have observed in many studies that in cancer, multiple vaccinations also work better against other viral infections than single vaccinations," she says.

The immune system often does not adequately respond to the first vaccination, with a second needed to prompt a robust immune response.

The problem with cancers, she adds, is that the weakened immune system both promotes more severe disease and responds worse to vaccination.

"Our observation is that a single vaccination can be strongly influenced by cancer therapy. This effect can be levelled out by multiple vaccinations - then it doesn't matter at what point during the therapy the vaccination takes place," the internist explains.

However, the success of vaccination is also strongly dependent on the type of cancer treatment.

A therapy that specifically targets the immune system - for example, in the case of blood cancer - leads to a significantly reduced immune response.

The evaluation also showed that antibody titer is not a good indicator of efficacy, von Lilienfeld-Toal says.

"About half of the studies we re-evaluated also measured the immune response of T cells, a group of immune cells that also specifically recognise antigens," she explains.

This method is not very standardised and is not routinely used. Nevertheless, it shows that even in the absence of antibody formation, specialised T cells are frequently developed against SARS-CoV-2.

With regard to possible risks for cancer patients, the study revealed that vaccination generally results in fewer side effects than COVID disease.

The risks are comparable to those of corresponding groups in the average population, and a negative effect on cancer was not observed in any of the studies. Notably, vaccination was associated with more pronounced radiotherapy complications in some cases.

In addition, a possible swelling of the lymph nodes after vaccination sometimes led to the erroneous assumption that new cancer foci had developed.

Therefore, recent vaccination should be considered during monitoring of cancer status.

Source: The Leibniz Institute for Natural Product Research and Infection Biology – Hans Knöll Institute