Study design and setting

We conducted a retrospective cohort study of individuals referred to our fast-track suspected H&N cancer clinics. Our hospital is a leading NHS trust providing tertiary H&N cancer services, with a dedicated regional MDT. The study period covered 12 weeks between 16 December 2020 to 12 March 2021. Data was collected from the fast-track clinic referral forms and the electronic records.
Study population
All patients referred to our fast-track H&N cancer clinics during the study period were initially screened for their COVID-19 vaccination status, and the reason for referral. All patients with cervical CVAL (cCVAL) were included. We defined cCVAL as any unilateral and lower cervical lymphadenopathy (level IV or V), first noticed within two weeks of COVID-19 vaccine injection in the ipsilateral deltoid muscle. All patients with bilateral, upper cervical, or known previous history of cervical lymphadenopathy were excluded. We also excluded patients if they received any other injection in the ipsilateral deltoid muscle within four weeks before the onset of lymphadenopathy.