A world-first study has found that children and adolescents undergoing chemotherapy responded well to the COVID-19 vaccination.
Associate investigator Dr Amy Body said, pleasingly, most of the children in the study had a good immune response to mRNA COVID-19 vaccines, with both antibodies and a type of white blood cell, called T-cell responses, detected.
The medical oncologist at Monash Health said the objective of the trial was to understand how well the COVID-19 vaccine works in children with cancer, who are often undergoing treatments that reduce their immune responses.
‘Due to their treatment, these children are at increased risk of becoming severely unwell with COVID-19. But the information regarding the effectiveness of vaccination for these children was limited,’ she said.
Prior to this study, the universal recommendation for children undergoing cancer treatment was to avoid vaccination, except for the seasonal flu vaccine, which is strongly recommended for both the child and their family members, said Associate Professor Peter Downie AM, who led the children’s cohort in this study.
‘We know that childhood immunity is adversely affected by chemotherapy.’
‘But now we have evidence that immunisation during treatment is effective and it needs further study with the other usual childhood infections that we have vaccines for,’ A/Prof Downie, a consultant paediatric haematologist-oncologist at Monash Children’s Hospital.
The study, published in The American Academy of Paediatrics, enrolled 113 patients, with the majority currently receiving cancer treatment, and found a positive neutralising antibody response in the majority of participants (two-thirds of patients responded after 2 doses, and more than three-quarters responded after 3 doses).
‘This key finding contravenes the accepted belief that children on chemotherapy will not respond to vaccinations and may influence future vaccine recommendations,’ according to the published paper.
Adverse events were generally mild to moderate and did not cause a delay in the ongoing cancer treatment.
The patients were enrolled at 3 cancer centres in Australia, including Monash Children’s Hospital Cancer Centre.
Out of the 113 patients, 44 were diagnosed with Covid-19 after receiving 2 or more vaccination doses, and while 30% of them were hospitalised, none required supplemental oxygen or intensive care.
‘This study represents the largest reported cohort of children with solid and hematological cancers undergoing COVID-19 vaccination.
It also found that vaccine-related adverse effects did not result in treatment delays, although a slightly higher rate of side effects, such as fever, muscle pain, and chills, was noted in this cohort compared to the original trial conducted in healthy children.
Children with cancer may also have other reasons for fevers or muscle pain (related to their cancer treatment or disease), which may have contributed to the symptoms noted in the trial.
Dr Body highlighted that while the vaccine was safe for her patients, some had fevers after vaccination, which is important to note for oncologists who might wish to time the vaccine at times when a fever would be of less concern to avoid unnecessary hospitalisations.
She noted that her team found patients who were still undergoing chemotherapy were less likely to respond to vaccination compared to those who had completed treatment.
‘But it is still reasonable to offer vaccination to all children during treatment, but be aware that some children are less likely to respond, and additional measures to protect against infection should be taken,’ said Dr Body.
The paper concluded that its data suggest vaccination during treatment may be more effective than previously thought, supporting the administration of primary vaccinations during treatment and booster doses at completion, rather than deferring vaccination altogether.
However, it added one caveat to vaccinating patients undergoing treatment: to avoid live vaccines, such as measles, mumps, rubella, and varicella, due to safety concerns.
The study also noted that mRNA vaccines used in this study differ from current childhood vaccinations and may have a greater ability to stimulate the immune system compared to traditional vaccinations.
Dr Body said her team believes that this study’s findings could be translated to other childhood vaccinations, which are often deferred until intensive treatment has been finished.
Agreeing, Dr Downie noted that the findings of this study are especially important in light of the current concerning rise in anti-vaccine lobby.
