Ômicron causes less severe conditions even in the elderly, study suggests

Infections caused by the omicron variant of the new coronavirus represent less severe cases when compared to those caused by delta, according to an American study. The analyzes carried out show that, even in the elderly, the new strain represented a lower risk of complications from the disease.

Signed by six researchers from the United States, most of them from the School of Medicine at Case Western Reserve University in Ohio, the study was published on the medRxiv platform and is a pre-print, that is, it has not yet been peer-reviewed.

For the investigation, the researchers accessed information from TriNetX, a platform that compiles data from more than 80 million patients from 63 health services across the United States.

Scientists focused on information from three periods of 2021 to compare delta and omicron impacts on the severity of Covid-19 cases.

The first interval covered data from September 1st to November 15th, a period that corresponds to the prevalence of delta in the country. In total, more than 560,000 cases of Sars-CoV-2 were compiled, according to the database used by the research.

The second was from 15 to 24 December, when omicron already had large community transmission in the country. In this case, about 14 thousand diagnoses of the disease were registered.

Finally, the period from 16 to 30 November was observed, when delta was still prevalent, but omicron had already been registered in the country. Approximately 78,000 infections were reported at that time.

Information on the predominance of variants in each of the intervals was based on epidemiological data from the CDC (Center for Disease Control and Prevention) in the United States. That is, the researchers did not perform genetic sequencing for the research.

This division was important to compare the impacts of the two variants, when each of them had a higher prevalence of infections, for severe cases of the disease. In the study, four aspects were selected to analyze the seriousness of Covid-19: search for an emergency medical service, hospitalization, admission to the ICU and use of mechanical ventilation.

These four factors were greater in periods of great dissemination of delta and there was a reduction in the interval in which omicron already had community transmission. For example, the percentage of cases requiring hospitalization during the Omicron wave of infection was less than half that of Delta.

Similarly, the search for emergency services dropped by approximately a third when observing the spread of the two variants, falling from 15% in the delta prevalence period to less than 5% in the case of omicron, which may indicate the less seriousness of this variant.

Another detail that the study paid attention to was the age groups of the infected people.

There was an age separation that made it possible to investigate whether omicron and delta represented a greater risk depending on age.

In this part of the study, it was not possible to apply the stratification by age group in relation to admission to the ICU or the adoption of mechanical ventilation due to a “small sample size”, being restricted to cases of hospitalization and emergency search.

The researchers found that there was a decrease in these two points during the prevalence of omicron in all age groups, even in people over 65 years, who had almost double these two complications during the period of greatest spread of the delta.

To ensure that the difference in Covid’s severity did relate to the two variants, the scientists also compared the two periods of highest prevalence of delta — the first when the omicron was not yet present in the country and the second when the new strain was already present. it had been registered in the United States, but still not widely dispersed.

Therefore, it was concluded that there was no significant decrease in the percentage of severe cases in the two moments dominated by the delta, indicating that possibly the reduction in emergency search, hospitalization, hospitalization and use of mechanical ventilation is actually associated less risk than omicron poses even in older people.

However, ensuring this situation is not yet possible with this study, says Raquel Stucchi, an infectious disease specialist and professor at Unicamp (University of Campinas). She says there are two points that weren’t covered so well in the investigation.

The first one is in relation to immunization. According to the article, it was not possible to effectively collect vaccine adherence through the survey database because there was “only about 2% [da taxa de vacinação documentada]”, even though there are indications that a larger portion of the population was already vaccinated in the periods that the study analyzed.

For Stucchi, the lack of this data makes it impossible to indicate whether the decrease in severe cases in the period of omicron prevalence was really caused by the variant being less severe. She says that it is possible that, with the arrival of the new strain, people were more concerned about getting vaccinated, making complications less likely due to greater adherence to the immunization campaign.

“[A questão] that we have [na questão da] lower omicron gravity [é] because the variant has so many mutations that it is easier to transmit, but it has less capacity to produce disease by itself or how much [a diminuição de casos graves] it is a benefit of vaccination,” he says.

Another aspect that Stucchi points out of the study is the interval determined by scientists for a patient to have complications from the coronavirus. According to the article, right after diagnosis, the infected person would need to have one of the four severity factors within three days to enter the percentage of patients with some severity. It is from there that the differences between the complications caused between delta and omicron were calculated.

The infectious disease specialist, however, claims that this interval for analysis could be longer as patients could develop more severe symptoms after three days — something that could indicate a change in the analysis of omicron severity in relation to delta.

“This study itself, for the period they chose for observation [de três dias], does not allow us to ratify the lower severity and lower risk of serious illness [ômicron]”he says.

Even so, the professor mentions that the research is a good indication to demonstrate that the new strain of coronavirus may not be so serious for different age groups.

“The study has a very expressive number and brings an indication that the disease really is less serious, particularly in the elderly”, he concludes.