Severe breakthrough COVID-19 infections in Scotland-implications for immunisation programmes

• Authors: Eyal Leshem, The Chaim Sheba Medical Centre; Kristin Nelson, Emory University; Benjamin Lopman, Emory University
• Journal Title: LANCET RESPIRATORY MEDICINE
• Volume: Volume 9, Number 12
• Publisher: ELSEVIER SCI LTD | 2021-11-30, Pages 1354-1356
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1016/S2213-2600(21)00413-6
• Subjects: Health Sciences, Medicine and Surgery
• Keywords: Science & Technology; Life Sciences & Biomedicine; Critical Care Medicine; Respiratory System; General & Internal Medicine; BNT162B2; VACCINE

Abstract

Clinical trials of the BNT162b2 mRNA (Pfizer–BioNTech) and ChAdOx1 nCoV-19 adenoviral (Oxford–AstraZeneca) vaccines showed high efficacy against symptomatic infection; however, evidence continues to emerge regarding protection against severe disease, hospitalisation, and death under real-world conditions. In December, 2020, the vaccines were approved in Scotland and rolled out, starting with health-care workers and the most vulnerable populations. At the time, the UK vaccination programme advised an extended dosing interval of 8–12 weeks, rather than the shorter 3-week interval used in the trials, to maximise coverage with a first dose quickly amid restricted vaccine supply. Since their introduction, early evaluations of COVID-19 vaccines, albeit with short follow-up, have shown excellent effectiveness in preventing severe outcomes.1 Breakthrough infections (in vaccinated people) were rare.2 Later assessments, since the surge in cases associated with the Delta variant, have reported increasing infection rates and breakthrough infections.3, 4 Factors such as waning immunity and strain-specific decline in vaccine effectiveness (immune escape) might contribute to breakthrough infections.4, 5 Overall risk for severe outcome comprises the risk of becoming infected (higher in health-care workers with greater exposure, for example) and the risk of deteriorating upon infection (higher with increasing age). Characterising people at the greatest risk of severe breakthrough infections, hospitalisation, and death is critical to promote targeted interventions, aimed at enhancing protection of vulnerable populations. Moreover, establishing the risks associated with alternative dosing schedules can support the adoption of such schedules in other countries that aim to maximise population-level protection given a restricted number of available vaccine doses.