The end of the COVID-19 pandemic

Abstract

There are no widely accepted, quantitative definitions for the end of a pandemic such as COVID-19. The end of the pandemic due to a new virus and the transition to endemicity may be defined based on a high proportion of the global population having some immunity from natural infection or vaccination. Other considerations include diminished death toll, diminished pressure on health systems, reduced actual and perceived personal risk, removal of restrictive measures and diminished public attention.

A threshold of 70% of the global population having being vaccinated or infected was probably already reached in the second half of 2021. Endemicity may still show major spikes of infections and seasonality, but typically less clinical burden, although some locations are still hit more than others. Death toll and ICU occupancy figures are also consistent with a transition to endemicity by end 2021/early 2022.

Personal risk of the vast majority of the global population was already very small by end 2021, but perceived risk may still be grossly overestimated. Restrictive measures of high stringency have persisted in many countries by early 2022. The gargantuan attention in news media, social media and even scientific circles should be tempered.

Public health officials need to declare the end of the pandemic. Mid- and long-term consequences of epidemic waves and of adopted measures on health, society, economy, civilization and democracy may perpetuate a pandemic legacy long after the pandemic itself has ended.

INTRODUCTION

Claiming a time-stamped end-date for the COVID-19 pandemic is precarious. There is no rigorously quantitative definition of pandemics, let alone their end.^{1, 2} In dictionary terms, a pandemic is ‘an epidemic occurring worldwide, or over a very wide area, crossing international boundaries and usually affecting a large number of people’.³

To avoid naming ‘pandemics’ all seasonal viral waves, unusual severity (death toll, healthcare burden) may be sought. However, not all new viruses that become widely spread have high clinical burden. Thus, one may call the wide spread of a new virus (against which populations have little prior immunity) a pandemic, regardless of severity. One has to define carefully how the term ‘pandemic’ is used to avoid misunderstandings. Once a high population immunity threshold (from infection or vaccination) is attained, the pandemic transitions to an endemic phase.

Selecting any quantitative immunity threshold is arbitrary. Thresholds defined on basic reproduction number considerations (1−(1/R₀)) make a lot of assumptions, do not allow properly for population heterogeneity, depend on R₀ estimates that may not be accurate and are expected to change when variants with different R₀ emerge and become dominant. Realistically, the threshold should be high, but not 100%. Probably, considerable population segments will remain unvaccinated despite all vaccination campaign efforts, and some unvaccinated people may still escape infection for many years. For noneradicated infectious agents, community transmission continues with recurrent seasonal waves and spikes of various heights in the endemic phase and with large differences across countries and locations. Despite high vaccination and prior infection rates, immunity may be insufficient to protect from mild infection and transmission (even less so, when new variants emerge), but may still markedly decrease serious outcomes.⁴

If transition to SARS-CoV-2 endemicity requires a prior vaccination/infection threshold of 70%, this threshold was probably already reached globally during 2021, as discussed below. However, several other considerations should be evaluated before safely relegating the pandemic to the past. These include the persisting death toll, clinical burden, actual and perceived personal risk, continuing measures taken against COVID-19, public attention and the legacy of both epidemic waves and adopted measures.

POPULATION IMMUNITY

By end 2021, 58% of the global population had received some vaccine and 49% had been fully vaccinated⁵ (although ‘fully’ may be a misnomer in the long-run). The proportion of people infected has uncertainty, because only a minority of infections are documented by testing.⁶ Based on almost 3000 seroprevalence estimates generated in various surveys to-date,⁷ probably 35–55% of the global population had been infected at least once by end 2021. By end 2021, probably 73–81% of the global population had been vaccinated, infected or both (Table 1). This may be even an underestimate. Therefore, a 70% threshold for the end of pandemic was already crossed during 2021 and SARS-CoV-2 entered its endemic phase. Massive Omicron variant surges since late 2021 added far more infections but were accompanied with lower mortality/clinical impact.^8–10 While Omicron may also be intrinsically less lethal, the picture could be largely explained also as an endemic escape variant surging against widespread background population immunity.

Source – https://onlinelibrary.wiley.com/doi/10.1111/eci.13782