The world is experiencing a large wave of infection with the omicron variant of SARS-CoV-2. Model-based estimates from the Institute for Health Metrics and Evaluation (IHME) suggest that around January 17, 2022, there were 125 million omicron infections per day globally, which is more than ten times the peak of the delta wave in April. of 2021.
The omicron wave is inexorably reaching all continents and only a few countries in Eastern Europe, North Africa, Southeast Asia and Oceania have not yet started their wave of this SARS-CoV-2 variant. The unprecedented level of infection suggests that more than 50% of the world will have been infected with omicron between the end of November 2021 and the end of March 2022.
Although IHME models suggest that global daily SARS-CoV-2 infections have increased more than 30-fold from late November 2021 to January 17, 2022, reported cases of COVID-19 in this period have only increased six-fold. times.
As the proportion of asymptomatic or mild cases has increased compared to previous variants of SARS-CoV-2, the overall infection detection rate has decreased worldwide from 20% to 5%.
Understanding omicron burden crucially depends on the proportion of asymptomatic infections. A systematic review based on previous SARS-CoV-2 variants suggested that 40% of infections were asymptomatic .
Evidence suggests that the proportion of asymptomatic infections is much higher for omicron, perhaps up to 80 to 90%. Garrett and his colleagues found that among 230 patients in South Africa who enrolled in a clinical trial, 71 (31%) tested positive by PCR for SARS-CoV-2 and had the omicron variant and had no symptoms.
Assuming this infection prevalence was representative of the population, the implied incidence compared to detected cases suggests that more than 90% of infections were asymptomatic in South Africa . The UK Office for National Statistics (ONS) Infection Survey estimated a point prevalence of PCR-positive SARS-CoV-2 infection of 6 to 85% for England on 6 January 2022.
In addition to the much higher proportion of asymptomatic infections, in the US the proportion of COVID-19 hospitalizations to detected hospitalized cases has decreased by approximately 50 % in most states compared to previous peaks .
The proportion of hospitalized COVID-19 patients requiring intubation or dying has decreased by up to 80-90% in Canada and South Africa.
Despite the reduction in disease severity from infection, the massive wave of omicron infections means that hospital admissions are increasing in many countries and will double or more than double the number of COVID-19 hospital admissions from previous increases in some countries according to IHME models.
In countries where all hospital admissions are tested for COVID-19, a substantial proportion of these admissions will be among people who present to hospital for reasons other than COVID-19 and who have asymptomatic SARS infection. CoV-2 . However, infection control requirements place greater demands on hospitals. Given the population prevalence of SARS-CoV-2 infection of more than 10%, as reported by the ONS infection survey in London, England, large numbers of healthcare workers are testing positive and should be contacted. quarantine, which puts double pressure on hospitals. Countries will need to prioritize supporting health systems in the next 4 to 6 weeks. However, data from Greece offers hope that severe COVID-19 outcomes from the omicron wave are limited; From December 21, 2021 to January 17, 2022, COVID-19 cases increased nearly 10-fold, but hospital intubations among hospitalized COVID-19 patients remained the same as in December.
Surprisingly, IHME models suggest that the intensity of omicron transmission is so high that policy actions—for example, increasing mask use, expanding vaccination coverage in unvaccinated people, or administering third doses of COVID vaccines— 19, taken in the coming weeks will have a limited impact on the course of the omicron wave. IHME estimates suggest that increasing mask wearing to 80% of the population, for example, will only reduce cumulative infections over the next 4 months by 10%.
Increasing COVID-19 vaccine boosters or vaccinating people who have not yet been vaccinated is unlikely to have a substantial impact on the omicron wave because by the time these interventions are scaled up, the omicron wave will largely be over. . Only in countries where the omicron wave has not yet started, the expansion of mask wearing before the wave may have a more substantial effect. These interventions still work to protect people from COVID-19, but the speed of the omicron wave is so rapid that policy actions will have little effect on its course globally in the next 4 to 6 weeks. The omicron wave appears to peak 3 to 5 weeks after the exponential rise in reported cases begins.
As of January 17, 2022, omicron waves have peaked in 25 countries in five WHO regions and 19 US states. The omicron peak is expected to occur in most countries between now and the second week of February 2022.
The latest omicron peaks are expected to occur in countries where the omicron wave has not yet started, such as Eastern Europe and Southeast Asia. Actions to increase testing for SARS-CoV-2, for example, are likely to increase disruption by having more people excluded from work or school, but are unlikely to affect the course of the omicron wave. In the era of omicron, I think COVID-19 control strategies need to be reset. Given the speed and intensity of the omicron wave, efforts to contact the trace appear to be futile in my opinion .
One question remains regarding countries pursuing zero COVID-19 strategies, such as China and New Zealand. China has local omicron transmission in January 2022. Given the high transmissibility of omicron, it seems unlikely that China or New Zealand will be able to permanently exclude the omicron wave. For countries with zero COVID-19, the question will be one of time. Subsequent waves of omicron will allow for further progress in increasing vaccination coverage and a better understanding of the impact of the omicron variant on an immunologically naïve population .
By March 2022, a large proportion of the world will have been infected with the omicron variant. With continued increases in COVID-19 vaccination, the use in many countries of a third vaccine dose, and high levels of infection-acquired immunity, global levels of immunity against SARS-CoV-2 should for some time. be at its highest point. For a few weeks or months, the world should expect low levels of virus transmission.
I use the term pandemic to refer to the extraordinary efforts of society over the past 2 years to respond to a new pathogen that has changed the way people live their lives and how policy responses have developed in governments around the world. world. These efforts have saved countless lives around the world. New variants of SARS-CoV-2 will surely emerge and some may be more serious than omicron. Immunity, whether derived from infection or vaccination, will wane , creating opportunities for continued transmission of SARS-CoV-2. Given seasonality, countries should expect higher potential transmission in the winter months .
However, the health impacts of future SARS-CoV-2 transmission will be minor due to extensive prior exposure to the virus, vaccines regularly adapted to new antigens or variants, the advent of antivirals, and the knowledge that The vulnerable can protect themselves during future waves when necessary by using high-quality masks and physical distancing. COVID-19 will become another recurring disease that health systems and societies will have to manage.
For example, the number of deaths from omicron appears to be similar in most countries to the level of a bad Influenza season in northern hemisphere countries. The US Centers for Disease Control and Prevention estimated that the worst flu season over the past decade in 2017-18 caused about 52,000 Ifluenza deaths with a likely peak of more than 1,500 deaths per day.
The era of extraordinary measures by governments and societies to control the transmission of SARS-CoV-2 will be over. After the wave of omicrons, COVID-19 will return but not the pandemic.
