COVID-19 vaccine efficacy in a rapidly changing landscape

During the Delta and subsequent Omicron surges, this predominance of severe disease among the unvaccinated was repeatedly illustrated by the published illustrations from numerous hospitals showing the disproportionate number of unvaccinated patients admitted to the COVID-19 wards, critical care units, and on the ventilators.3 The other benefits of vaccination, such as reduction in detectable viral load and reduction in contagious period, are more difficult to measure on a population-wide level. Recent data also suggest that fourth vaccine doses in the general population again offer improved protection against infection and severe disease compared with three doses.7 The issue of the waning immunity of the population, especially at the extremes of age, and the issue of vaccine availability to the very young or the disadvantaged continue to require further investigation and appropriate action. 4 Centers for Disease Control and Prevention.