Introduction
The COVID-19 pandemic caused by the SARS-CoV-2 virus has resulted in millions of deaths and strained health-care systems all around the globe. Huge collaborative efforts led to the development and deployment of successful vaccinations that have shown to reduce the risk of severe infections and mortality.1-3 In the United Kingdom (UK), following a rigorous review of safety and efficacy data, the Pfizer/BioNTech was the first COVID-19 vaccine to be approved by the Medicines and Healthcare products Regulatory Agency (MHRA), followed by the Oxford/AstraZeneca and the Moderna vaccines.1-3 The rollout of COVID-19 vaccination in the UK, and in many other countries, prioritized those most likely to die from the disease especially older care-homes residents and immunocompromised adults, as well as protected health and social care workers.
Similar to other vaccines, local adverse drug reactions (ADRs) like shoulder pain and erythema, in addition to mild systemic symptoms like fatigue, myalgia and headache are commonly reported after COVID-19 vaccination.3-6 However, data from recent clinical trials and early post-marketing clinical experience have suggested a higher incidence of local lymphadenopathy reactions in the axilla and neck.3,5-7 With the widespread rollout of COVID-19 vaccination programmes, lymphadenopathy have created a diagnostic and therapeutic dilemma for cancer screening and diagnosis services.8-10 For this reason, the United States Society of Breast Imaging, the Canadian Society of Breast Imaging, the Canadian Association of Radiologists, and a multidisciplinary team (MDT) of experts from three leading cancer centres in the United States have all recently released emergency recommendations for the management of COVID-19 vaccine-associated lymphadenopathy (CVAL).7,10,11
Cases of ipsilateral lymphadenopathy in the lower neck and supraclavicular region following COVID-19 vaccinations are quickly emerging in the international literature, and certainly being increasingly referred to the healthcare services for advice and management.12-14 As lower neck lymphadenopathy usually harbours malignancy in around 75% of cases, the UK National Institute for Health and Care Excellence (NICE) recommended fast-track referral of unexplained or persistent cases through a dedicated pathway for suspected H&N cancer.15,16 The differential diagnosis of lymphadenopathy in the lower neck is broad, but it is imperative to exclude pathologies like head and neck (H&N) malignancy, lymphoma, and metastatic lung or cutaneous cancers.10,15 However, as vaccine deployment is still in its early stages, no data is yet available regarding the presentation, clinical course, or imaging characteristics of cervical COVID-19 vaccine-associated lymphadenopathy (CVAL) to guide the decision-making process in such patients. The presented work is the first study to report on the characteristics and clinical course of cervical lymphadenopathy following COVID-19 vaccination, with special emphasis on potential implications for the head and neck cancer services.

Methods