The world is experiencing a huge wave of infection with the omicron variant of SARS-CoV-2. Estimates based on Institute for Health Metrics and Evaluation (IHME) models suggest that on around Jan 17, 2022 there were 125 million omicron infections a day in the world, which is more than ten times the peak of the delta wave in April, 2021 says Christopher J L Murray, Director of IHME in a study published in The Lancet.
Although IHME models suggest that global daily SARS-CoV-2 infections have increased by more than 30 times from the end of November, 2021 to Jan 17, 2022, reported Covid-19 cases in this period have only increased by six times. Because the proportion of cases that are asymptomatic or mild has increased compared with previous SARS-CoV-2 variants, the global infection-detection rate has declined globally from 20 per cent to 5 per cent.
Evidence suggests that the proportion of asymptomatic infections is much higher for omicron, perhaps as high as 80-90 per cent, Murray says.
Despite the reduced disease severity per infection, the massive wave of omicron infections means that hospital admissions are increasing in many countries and will rise to twice or more the number of Covid-19 hospital admissions of past surges in some countries according to the IHME models. In countries where all hospital admissions are screened for Covid-19, a substantial proportion of these admissions will be among individuals coming to hospital for non-Covid-19 reasons who have asymptomatic SARS-CoV-2 infection.
Surprisingly, IHME models suggest that the transmission intensity of omicron is so high that policy actions—eg, increasing mask use, expanding vaccination coverage in people who have not been vaccinated, or delivering third doses of Covid-19 vaccines—taken in the next weeks will have limited impact on the course of the omicron wave.
IHME estimates suggest that increasing use of masks to 80 per cent of the population, for example, will only reduce cumulative infections over the next 4 months by 10 per cent. Increasing Covid-19 vaccine boosters or vaccinating people who have not yet been vaccinated is unlikely to have any substantial impact on the omicron wave because by the time these interventions are scaled up the omicron wave will be largely over. Only in countries where the omicron wave has not yet started can expanding mask use in advance of the wave have a more substantial effect.
"Given the speed and intensity of the omicron wave, in my view efforts to contact trace seem to be futile,"Murray says.
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, for some time global levels of SARS-CoV-2 immunity should be at an all time high. For some weeks or months, the world should expect low levels of virus transmission.
"I use the term pandemic to refer to the extraordinary societal efforts over the past 2 years to respond to a new pathogen that have changed how individuals live their lives and how policy responses have developed in governments around the world. These efforts have saved countless lives globally. New SARS-CoV-2 variants will surely emerge and some may be more severe than omicron. Immunity, whether infection or vaccination derived, will wane, creating opportunities for continued SARS-CoV-2 transmission. Given seasonality, countries should expect increased potential transmission in winter months," he added.
The impacts of future SARS-CoV-2 transmission on health, however, will be less because of broad previous exposure to the virus, regularly adapted vaccines to new antigens or variants, the advent of antivirals, and the knowledge that the vulnerable can protect themselves during future waves when needed by using high-quality masks and physical distancing. Covid-19 will become another recurrent disease that health systems and societies will have to manage. For example, the death toll from omicron seems 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 the worse influenza season during the past decade in 2017–18 caused about 52 000 influenza deaths with a likely peak of more than 1500 deaths per day.11 The era of extraordinary measures by government and societies to control SARS-CoV-2 transmission will be over. After the omicron wave, Covid-19 will return but the pandemic will not says the IHME director.