Background
Pneumonia is one of the main contributors to non-cancer mortality among patients with head and neck cancer (HNC). This study aimed to determine the vaccine uptake for pneumococcal polysaccharide and conjugate vaccines, quadrivalent influenza vaccines, and mRNA COVID-19 vaccines before and after an HNC diagnosis. Furthermore, the study investigated the timing of vaccination after a cancer diagnosis.

Materials & methods
This register based multicentre study included Danish patients ≥ 18y diagnosed with HNC between 2018 and 2021. The vaccine uptake was assessed by calculating cumulative incidence (CI), while the timing of vaccination after an HNC diagnosis was explored by calculating incidence rates of vaccination the first and second half year after a cancer diagnosis.

Results
The cumulative incidence of vaccine uptake for pneumococcal vaccines was estimated to be 8 % and 16 % one year before and after an HNC diagnosis, respectively. The CIs were 36 % and 38 % for quadrivalent influenza vaccines, respectively, whereas the CIs of vaccine uptake for mRNA COVID-19 vaccines were 60 % and 89 %. The IR of mRNA COVID-19 vaccinations the first half year after HNC diagnosis were 273 per 1000 person-months of follow-up (PMFU) and 111 per 1000 PMFU the second half year, respectively (IRR: 0.38, p < 0.001). Comparing the same periods, the IR of quadrivalent influenza vaccination was 28 per 1000 PMFU and 51 per 1000 PMFU (IRR: 1.95, 0 < 0.001). The IRs of pneumococcal vaccinations were 11 per 1000 PMFU and 14 per 1000 PMFU (IRR 1.28, p = 0.21).

Conclusions
Although our study shows a significant increase in pneumococcal and COVID-19 vaccine uptake after HNC diagnosis, a gap remains in vaccine uptake before diagnosis, underscoring the need for increased awareness of vaccination options and recommendations. Our findings could serve as a reference for future recommendations.