Director, Research Epidemiology Moderna, Inc. Cambridge, United States
Background: Four endemic human coronavirus (hCoV) strains, hCoV-229E, hCoV-OC43, hCoV-NL63, and hCoV-HKU1, cocirculate seasonally and are a substantial cause of acute respiratory illness. There is currently no vaccine against endemic hCoVs. Following the successful development of a vaccine for the pandemic novel coronavirus SARS-CoV-2, questions have arisen surrounding the potential benefit of a vaccine to protect against endemic hCoVs as well.
Objectives: To synthesize the literature on the molecular epidemiology, occurrence, risk factors, and natural history of the four commonly circulating endemic hCoV strains with the intent of informing the composition, need, and potential impact of a vaccine for seasonal hCoVs.
Methods: A systematic literature search was conducted in PubMed and EMBASE combining search terms for human coronaviruses and topic areas of interest (e.g. incidence, severity, mortality). Articles were restricted to those published from 2005-2022 in the English language. Deduplicated articles were reviewed for relevance and categorized into article type, data source/setting, age of study population, and geography.
Results: The systematic search produced 3,632 unduplicated articles, of which 530 were selected for review and 194 were included in the epidemiologic synthesis. Endemic hCoVs are common, with most individuals seroconverting to at least one endemic hCoV strain by age 2 or 3 years. Combined, endemic hCoVs represent the second or third most common pathogen in respiratory illnesses and have an estimated population-based incidence of 5 to 20 infections per 100 person-years and an estimated medically-attended incidence of 1 to 13 per 1,000 population. Endemic hCoVs are most often detected in infants, children under 5 years, and older adults, though the highest severity occurs in older adults, particularly those with comorbidities. By strain, OC43 is most common among medically attended cases, 229E is often most severe and occurs more often in older age groups, and NL63 is more common in children than adults. Repeated studies observed an alternating frequency between OC43 and HKU1 (betacoronaviruses) and NL63 and 229E (alphacoronaviruses), resulting in biennial peaks for each.
Conclusions: A vaccine against endemic hCoVs could help mitigate one of the largest causes of acute respiratory illness globally, reducing morbidity, missed work and school, and severe complications among individuals with comorbidities. The findings from this systematic review can be used to inform demographic, clinical, and strain-specific decisions required for successful vaccine development.
