Childhood Cancer Survivors Face Higher COVID-19 Severity Risk

Adults who survived childhood cancer face a 58% higher risk of severe COVID-19 complications, even decades after their original diagnosis, according to a comprehensive study tracking over 13,000 survivors across Denmark and Sweden.

The research reveals that while these survivors were less likely to contract COVID-19 initially, their outcomes proved significantly worse when infection did occur.

The findings challenge assumptions about long-term cancer survivor health and highlight how childhood treatments can create lasting vulnerabilities. Despite having higher vaccination rates than the general population, childhood cancer survivors required hospitalization, intensive care, or died from COVID-19 at substantially higher rates.

Decades-Long Health Impact

“It is important to understand that even though these individuals were not infected more often, the consequences were more serious when they did become ill,” emphasized Javier Louro, postdoctoral researcher at Karolinska Institutet and the study’s lead author.

The research, published in The Lancet Regional Health – Europe, tracked survivors for three years from January 2020 through December 2022. The study population included people who had been diagnosed with cancer before age 20 and were at least 20 years old when the pandemic began, with an average age of about 41 years.

Researchers compared the survivors against both randomly selected individuals from the general population and their own siblings, providing robust control groups that accounted for both population-wide and family-specific factors.

Pandemic Waves Revealed Vulnerability

The heightened risk became particularly evident during periods of widespread viral transmission. Initial differences were subtle, but as new variants like Alpha and Omicron emerged, the gap in severe outcomes widened dramatically between survivors and comparison groups.

Key findings from the study include:

• Survivors 50 years or older showed an 85% higher risk of severe COVID-19
• Those diagnosed with cancer at age 15 or older faced more than double the risk
• Solid tumor survivors had a 63% higher risk compared to general population
• Risk differences were most pronounced from July 2021 onward, with survivors showing 2.35 times higher severe COVID-19 risk

Country Differences Reveal Policy Impact

Comparing Denmark and Sweden provided unique insights into how pandemic management strategies affected vulnerable populations. Sweden’s more permissive approach—relying on recommendations rather than mandates—corresponded with consistently higher risk ratios for survivors compared to Denmark’s stricter early restrictions.

However, both countries ultimately reached similar cumulative rates of severe COVID-19 among survivors by the study’s end, suggesting that pandemic control measures may have influenced the timing rather than the overall impact.

The research utilized Nordic countries’ comprehensive health registries, which capture nearly complete population data with minimal loss to follow-up. This registry-based approach eliminated common biases associated with self-reported data or selective participation.

Clinical Implications for Future Preparedness

“Our results suggest that childhood cancer survivors should be considered a risk group in future pandemics or other health crises,” Louro noted. “This could involve prioritising them for vaccination or offering special protection during periods of high transmission.”

The findings extend beyond COVID-19, with implications for seasonal influenza and other infectious diseases. The study authors emphasize that the vulnerability persists many years after cancer treatment, suggesting that survivors’ immune systems may remain compromised long-term.

Notably, survivors actually showed more cautious behavior during the pandemic, with lower overall infection rates despite their increased vulnerability to severe outcomes when infected. This suggests that risk awareness and protective behaviors may have helped limit exposure.

The research comes as the population of childhood cancer survivors continues growing due to improved treatments, with five-year survival rates now exceeding 85% in high-income countries. This growing survivor population represents an important consideration for public health planning and emergency preparedness.

The study was supported by Danish and Swedish childhood cancer foundations and research councils, reflecting the collaborative Nordic approach to understanding long-term health outcomes in cancer survivors.