Omicron: Hospitalization Risks And Factors

Several studies have found that the Omicron variant of COVID-19 is less likely to result in hospitalisation when compared to the Delta variant. A study out of Scotland found that the risk of hospitalisation was two-thirds less with Omicron than with Delta. However, it is important to note that the majority of Omicron cases in the study were among younger adults, who are generally less likely to develop severe cases of COVID-19. While the findings suggest that Omicron may be less severe than Delta, experts caution that Omicron's higher transmission rate could still lead to an increase in the absolute number of people requiring hospitalisation.

Omicron is less likely to put you in the hospital than the Delta variant

Several studies have indicated that the Omicron variant is less likely to result in hospitalisation when compared to the Delta variant. A study out of Scotland, conducted by scientists at the University of Edinburgh, found that the risk of hospitalisation was two-thirds less with Omicron than with Delta. This study analysed nearly 24,000 Omicron cases, most of which were among younger adults aged 20 to 39, who are generally less likely to develop severe cases of COVID-19.

Matthew Binnicker, director of clinical virology at Mayo Clinic in Rochester, Minnesota, noted that the higher percentage of younger people in the Omicron group compared to the Delta group could have biased the conclusions towards less severe outcomes caused by Omicron. However, he acknowledged that the data suggests Omicron might lead to a less severe disease course.

Salim Abdool Karim, a clinical infectious disease epidemiologist in South Africa, where the Omicron variant was first detected, reported that the rate of hospital admissions was significantly lower for Omicron than for Delta. Additionally, an analysis from the Imperial College London COVID-19 response team estimated that people infected with the Omicron variant in England were around 20% less likely to require hospitalisation and 40% less likely to be hospitalised for a night or more compared to those infected with the Delta variant.

While these findings offer a positive outlook, it is important to recognise the limitations of the studies. The sheer number of Omicron infections, coupled with its higher transmission rate and ability to evade vaccines, could still overwhelm hospitals. Furthermore, the findings are specific to a particular point in time during a rapidly evolving pandemic, and other countries may experience different outcomes.

Omicron spreads faster than Delta

Several studies have shown that the Omicron variant of COVID-19 spreads faster than the Delta variant, especially among vaccinated individuals. A Danish study of nearly 12,000 households found that Omicron spreads 1.17 times faster than Delta among unvaccinated individuals, 2.61 times faster among fully vaccinated individuals, and 3.66 times faster among those who have received booster shots. The study also discovered that unvaccinated individuals spread the virus more easily than those who are fully vaccinated, while there was reduced transmission between people who received booster shots. The Omicron variant was found to evade the immunity of vaccinated individuals at a much faster pace compared to Delta, demonstrating strong evidence of the variant's immune evasiveness.

The high transmissibility of Omicron is attributed to its ability to evade vaccines more effectively than Delta. The effectiveness of vaccines is reduced to around 40% for symptoms and 80% for severe disease with the Omicron variant. Numbers improved with booster shots, as effectiveness was reduced only to 86% for symptoms and 98% for severe infection. The vaccination effectiveness of the Pfizer-BioNTech vaccine for preventing Omicron infection is only 35%.

The rapid spread of Omicron has resulted in a high number of infections, which has the potential to overwhelm hospitals despite the variant causing milder symptoms and fewer hospitalizations than Delta. Matthew Binnicker, director of clinical virology at Mayo Clinic in Rochester, Minnesota, emphasized that "if Omicron has a much higher transmission rate compared to Delta, the absolute number of people requiring hospitalization might still increase, despite less severe disease in most cases."

While the reduced severity of Omicron is encouraging, scientists stress that the high transmissibility and immune evasiveness of the variant need to be considered. "Cautious optimism is perhaps the best way to look at this," said Manuel Ascano Jr., a Vanderbilt University biochemist who studies viruses. The findings from these studies suggest that adapted or improved vaccines may be necessary to mitigate the spread of Omicron.

Omicron is more able to evade vaccines

Several studies have shown that the Omicron variant of COVID-19 is less likely to result in hospitalisation than the Delta variant. A Scottish study by scientists at the University of Edinburgh found that the risk of hospitalisation was two-thirds less with Omicron than with Delta. However, it was noted that the Omicron cases in the study were predominantly among younger adults, who are generally less likely to develop severe cases of COVID-19.

Despite this, the Omicron variant has been found to be more transmissible than previous variants, and its ability to evade vaccines and natural immunity means that it could still lead to a high number of hospitalisations. Early warnings from South Africa, where the variant was first detected, suggested that the rate of admissions to hospitals was far lower for Omicron than for Delta. However, South African scientists have since discovered new Omicron sublineages that are likely able to evade vaccines and natural immunity from prior infections. The BA.4 and BA.5 sublineages, in particular, appear to be more infectious than the original Omicron variant and early variants, and studies have shown that they are more likely to evade antibodies from vaccines.

The high transmissibility of Omicron and its subvariants means that a large number of infections could still overwhelm hospitals, despite the reduced severity of the disease in most cases. While the reduced severity of Omicron is encouraging, it is important to remain cautious as the situation is quickly evolving.

Omicron causes less severe disease

Several studies suggest that the Omicron variant of COVID-19 causes less severe disease and is less likely to put you in the hospital compared to previous variants, such as Delta.

A study out of Scotland by scientists at the University of Edinburgh found that the risk of hospitalization was two-thirds less with Omicron than with Delta. However, the study noted that the majority of Omicron cases in Scotland were among younger adults aged 20-39, who are generally less likely to develop severe cases of COVID-19.

Matthew Binnicker, director of clinical virology at Mayo Clinic in Rochester, Minnesota, noted that the higher percentage of younger people in the Omicron group compared to the Delta group could have biased the conclusions towards less severe outcomes. Nonetheless, he found the data interesting and suggested that Omicron might lead to less severe disease overall.

Data from South Africa, where the Omicron variant was first detected, also supports the idea that Omicron causes less severe disease. Salim Abdool Karim, a clinical infectious disease epidemiologist in South Africa, reported that the rate of admissions to hospitals was far lower for Omicron than for Delta, with an overall admission rate of 2-4% compared to 20% previously.

An analysis from the Imperial College London COVID-19 response team estimated that people infected with the Omicron variant in England were around 20% less likely to be hospitalized at all and 40% less likely to be hospitalized for a night or more compared to those infected with the Delta variant.

While the findings on the reduced severity of Omicron are encouraging, scientists stress that they need to be weighed against the fact that Omicron spreads much faster than Delta and is more able to evade vaccines. The sheer number of infections could still overwhelm hospitals. Therefore, a cautious optimism is warranted.

Omicron hospitalisations are higher in older adults

Several studies have shown that the Omicron variant is less likely to cause hospitalization than the Delta variant. However, it is important to note that the Omicron variant is more transmissible than Delta and can evade vaccines more easily. Therefore, the absolute number of hospitalizations might still increase due to the high infection rate.

While Omicron generally results in less severe disease, older adults, especially those in long-term care facilities, remain vulnerable to severe COVID-19 and breakthrough infections, even with high vaccination rates. This is because older adults, particularly those with frailty or residing in congregate settings, are at increased risk of SARS-CoV-2 Omicron infection and severe disease.

A study in Canada found that older adults in long-term care and retirement facilities with prior Omicron infection were at an increased risk of reinfection. This suggests that hybrid immunity from vaccination and infection may not provide sufficient protection against subsequent Omicron reinfections in this population.

Another study in Singapore found that boosting was associated with a decreased risk of COVID-19-related hospitalization across all frailty categories in older adults who were infection-naive. However, additional booster doses beyond the first one did not reduce the risk of hospitalization in infection-naive older adults with high-frailty risk.

In summary, while Omicron may be less likely to cause hospitalization than previous variants, older adults, especially those with frailty or residing in long-term care settings, are still at an increased risk of severe disease and hospitalization. The effectiveness of vaccination and boosting in this population requires further study, especially considering the evolving nature of hybrid immunity.

Frequently asked questions