Relaxing restrictions at the pace of vaccination increases freedom and guards against further COVID-19 waves

Abstract

Mass vaccination offers a promising exit strategy for the COVID-19 pandemic. However, as vaccination progresses, demands to lift restrictions increase, despite most of the population remaining susceptible. Using our age-stratified SEIRD-ICU compartmental model and curated epidemiological and vaccination data, we quantified the rate (relative to vaccination progress) at which countries can lift non-pharmaceutical interventions without overwhelming their healthcare systems. We analyzed scenarios ranging from immediately lifting restrictions (accepting high mortality and morbidity) to reducing case numbers to a level where test-trace-and-isolate (TTI) programs efficiently compensate for local spreading events. In general, the age-dependent vaccination roll-out implies a transient decrease of more than ten years in the average age of ICU patients and deceased. The pace of vaccination determines the speed of lifting restrictions; Taking the European Union (EU) as an example case, all considered scenarios allow for steadily increasing contacts starting in May 2021 and relaxing most restrictions by autumn 2021. Throughout summer 2021, only mild contact restrictions will remain necessary. However, only high vaccine uptake can prevent further severe waves. Across EU countries, seroprevalence impacts the long-term success of vaccination campaigns more strongly than age demographics. In addition, we highlight the need for preventive measures to reduce contagion in school settings throughout the year 2021, where children might be drivers of contagion because of them remaining susceptible. Strategies that maintain low case numbers, instead of high ones, reduce infections and deaths by factors of eleven and five, respectively. In general, policies with low case numbers significantly benefit from vaccination, as the overall reduction in susceptibility will further diminish viral spread. Keeping case numbers low is the safest long-term strategy because it considerably reduces mortality and morbidity and offers better preparedness against emerging escape or more contagious virus variants while still allowing for higher contact numbers (freedom) with progressing vaccinations.

What Happens to the Immune System after Vaccination or Recovery from COVID-19?

“…Confirmed cases, deaths and hospital admissions are sharply decreased in countries with a major population fully vaccinated [156]. Bauer et al (2021) reinforced that the safest longterm strategy is keeping a low number of COVID-19 cases to preserve reduced mortality and morbidity. This strategy creates better conditions in the case of emerging SARS-CoV-2 variants that can escape the immune system and as governments reduce restrictive measures with progressing vaccinations [157].…”

Interplay Between Risk Perception, Behavior, and COVID-19 Spread

“…In that way, an infectious disease outbreak will proliferate if the spreading rate of the disease is larger than the recovery rate and if a large-enough fraction of the population is susceptible to being infected. However, these simple models often tend to overestimate the size of an infectious disease outbreak or all possible trajectories for the incidence trends [23], as they do not incorporate mechanisms of dynamical adaptation of restrictions [25] or, as studied in this paper, behavior.…”

“…In line with what has been observed in high-income countries, we assume that vaccination rates are mostly limited by vaccine hesitancy instead of vaccine stocks or logistics. In that way, we can deal with emergent VOCs (as Omicron) with a healthy combination of mandatory NPIs aiming for low-case numbers while a working vaccine is developed and coverage is insufficient [25,48] and by letting individuals decide on their own when the roll-out is complete. However, the core problem remains latent; wealthy countries concentrate resources while some countries cannot afford enough vaccines to protect even their population at risk [59].…”

“…The scenarios end in April, where we expect that an updated booster vaccine is developed and distributed. In that phase, lifting restrictions at the pace of vaccination and aiming for low case numbers would maximize freedom while minimizing mortality and morbidity [25,[48][49][50].…”

COVID-19 vaccine perceptions in the initial phases of US vaccine roll-out: an observational study on reddit

“…On August 23, 2021, The US FDA issued a Letter of Approval to Pfizer for full use of the vaccine, under the name COMIRNATY for use in persons aged 16 years and older and delayed pediatric approval for those younger than 12 years [ 2 ]. From early 2021 on, COVID-19 vaccines have helped alleviate the pandemic’s burden on society by mitigating contagion, protecting the population against severe disease, and allowing for less restrictive measures, especially in countries with high vaccine uptake and availability [ 3 ]. Since mid-2021, vaccine availability does not pose a problem in high-income countries.…”