The Combined Effect of Vaccination and Nonpharmaceutical Public Health Interventions-Ending the COVID-19 Pandemic.

Abstract

Since the emergence of the first cases of SARS-CoV-2 infection in late 2019 and the declaration of a global pandemic in March 2020, the public health and economic impacts of the COVID-19 pandemic have been substantial. The impact of the pandemic is being felt around the world, and in its early stages, only a few countries were successful in limiting community transmission by early and proactive public health measures aimed at preventing importation and seeding of infection in their jurisdictions. As we collectively learned about this new pathogen and its transmission routes and patterns, most countries relied on public health measures based on previous experience of epidemics of respiratory pathogens with human-to-human transmission to mitigate the effects of COVID-19 infection. These measures included isolation and quarantine, stay-at-home orders, closure of nonessential businesses and schools, physical distancing, limiting social interactions, and enhanced respiratory hygiene, collectively known as nonpharmaceutical interventions (NPIs). These interventions were later supplemented by the recommendation and/or mandate that the public wear nonmedical masks with the aim of reducing transmission at the population level.1 As unintended consequences and the economic toll of public health restrictions continue to mount, a strategy to end this pandemic logically involves deploying effective and safe vaccines. There are several vaccines, mostly based on messenger RNA and nonreplicating viral vector technologies, now approved for use by regulatory authorities around the world. Because the rollout of vaccination campaigns around the world still depends on vaccine supply and available public health infrastructure, it is only natural to ask when we can roll back public health NPIs. Elsewhere in JAMA Network Open, Patel et al2 describe an agent-based mathematical modeling approach to simulate several scenarios of different vaccine effectiveness and vaccine coverage associated with maintaining or discontinuing NPIs within a large representative sample of a synthetic population (agents) of more than 1 million people in North Carolina. The population was further stratified by ethnicity/race and urban/suburban/rural settings based on census data. The model was parameterized to characterize the underlying transmission dynamics of SARS-CoV-2 infection and calibrated and validated against public health surveillance data in North Carolina. Vaccination was implemented in the model during 6 months by transitioning individuals into a recovered/immune state. The NPIs represented in the model included quarantine, school closures, social distancing, and mask wearing, which were modeled by implementing the reduction in transmission rates associated with these interventions over time. By generating the model’s projections of the number of infections, hospitalizations, and deaths during an 18-month period and comparing these outcomes for several scenarios, the authors found some interesting results. First, it is apparent that lifting NPIs while rolling out vaccinations was associated with a significant increase in the number of infections, hospitalizations, and deaths across the range of vaccine effectiveness and vaccine coverage assumptions. Second, achieving a higher vaccine coverage leads to a greater reduction in the number of infections, even with the relatively lower vaccine effectiveness in the absence of NPIs with a combination of 75% coverage and 50% efficacy, resulting in a greater risk reduction compared with 25% coverage and 90% efficacy. Third, the cumulative incidence of infections, hospitalizations, and deaths varied by ethnicity/race and place of residence across different scenarios, with African American persons and residents of rural areas faring the worst.2 + Related article