Three different studies indicate that Omicron infections have lower hospitalization rates but among hospitalized patients there are no differences between one strain and another in terms of disease severity. Recent immunization is highly protective
Three different teams of scientists have found that Omicron infections cause mild illness more often than previous variants of the coronavirus.
Could the surge in Omicron cases taking place all over the world therefore not be so catastrophic for the individual?
A study of‘Imperial College London confirms a lower rate of hospitalizations: 40-45% less than Delta. Research from Scotland talks about 66% lower hospitalization rates and another from South Africa talks about 70-80% fewer hospitalizations. This latest work however highlights that once patients are hospitalized there are no differences between infected with the Omicron variant and infected with other variants, as regards the severity of the disease.
The three papers concluded that the new strain registers lower hospitalization rates but Omicron’s lower risk of hospitalization in all three countries appears to be largely due toacquired immunity: many of those infected were protected from serious illness due to previous infections or vaccinations. In summary (and the data is very explicit in the South Africa study) less people end up in hospital thanks to previous (and recent) vaccines and infections, but there are no differences in the severity of the disease among the hospitalized. The difference isrecent immunization (booster) which makes the case and hospitalization ratio favorable, mitigating the potentially disastrous effect of the high diffusion capacity of this variant
At the moment it therefore seems difficult to establish with certainty whether the virus has really weakened or if the lower severity of cases depends on the fact that the population is immunized thanks to vaccines or previous infections, as these latest studies seem to suggest anyway. The other problem that worries scientists and governments around the world is that the virus runs very fast: according to another work from Imperial College Omicron refines 5.4 times more than Delta. Furthermore, the incubation time appears to have been reduced to just three days. This means that even if the probability of hospitalization for Omicron variant is lower than for Delta, hospitals risk collapse due to the high diffusivity.
We know from another preliminary laboratory work from Hong Kong that Omicron replicates much better than Delta in the bronchi, but not in the lungs. More in detail, the variant multiplies about 70 times faster inside the bronchi than the Delta variant and reaches high levels of concentration in this area quickly: 48 hours after infection. The good news is that in lung tissue the variant proved to be about 10 times less efficient than Delta and this is the detail thatand suggests how Omicron could cause less severe disease.
Does Omicron have biological characteristics that make it less dangerous than Delta?
Scientists have monitored the infection of the virus only for a period of 48 hours and to have confirmation – the scholars warn – we need consolidated data on the real world. The three mentioned above are all preliminary and in pre-print but can begin to give an idea
The South African study has focused on increasing Omicron cases since November. The Rrisk of hospitalization was 70% lower among people infected with Omicron compared to those infected with other variants. The authors speculate that the milder cases could be due to the fact that Omicron manages to infect many people who have already contracted Covid or have been vaccinated, widening (greatly) the audience of the susceptible. Although the variant manages to evade acquired immunity, the vaccine and infection are still able to protect against severe disease and this would explain the apparent lower virulence. “Omicron may seem milder, without changing its virulence, but it could only be appearance” he explains Natalie E. Dean, professor of biostatistics, specializing in infectious diseases and vaccines at the Rollins school of public Health. “THEThe denominator for calculating severe cases also includes reinfections. With a variant with a high capacity for reinfection, the severity of cases has not changed among the susceptible population: it is always severe, moderate, mild, asymptomatic. Only now we see reinfections and these are generally not serious ».
The same authors caution that the data was collected during the early stages of the Omicron wave, when the infection rate was low overall and people with mild symptoms were more likely to be hospitalized at that stage before wards filled.
But the important fact that emerges from the South African study – the scientist also points out Eric Topol – is that a decrease in disease severity is observed compared to the previous Delta wave, but not between Omicron and the other variants in the current wave. According to the authors, the decrease in severity between the previous wave and the current one is to be found at least in part at the high levels of immunity recently reached by the population.
In Scotland , the researchers looked at the Delta and Omicron cases in November and December, looking at how many patients with each variant were hospitalized. The researchers found that Omicron infections are associated with a two-thirds reduction in hospitalization risk compared to the Delta variant. Mark Woolhouse, professor of infectious diseases at the University of Edinburgh and co-author of the new study warns: “Even if these results are confirmed by the dramatic wave of Omicron, involving many people it will still cause many hospitalizations and bring hospitals into serious difficulties.”
The work of the researchers of theImperial College London compared the cases of Omicron and Delta in the first two weeks of December and reported a reduction in hospitalizations although lower than that seen by Scottish colleagues. The data suggests that compared to cases with the Delta variant, people infected with Omicron are on average 15 to 20 percent less likely to report to hospital and 40 to 45 percent less likely to spend one or more nights in hospital. Furthermore, those who have already been infected previously have a 50-60% less chance of hospitalization than those who have not been previously infected, confirming that theacquired immunity helps make Omicron infections milder on average.
However, as he points out on Faceboook
Enrico Bucci, professor of Biochemistry and Molecular Biology at Temple University in Philadelphia “the apparent reduction in the risk of hospitalization, if the previous immunity status of the infected is properly considered, is not recorded.” Once the confounding effects due to age, gender, preexisting immunization and other variables have been analyzed, the probability of hospitalization is currently estimated after infection with Omicron it is not significantly different from that after infection with other variants.
James Naismith, director of the Rosalind Franklin Institute and professor of structural biology, University of Oxford pointed out: ‘This study finds that previous infection reduces the risk of hospitalization by about two thirds. thus indicating that Omicron is milder if you have some immunity. However, research suggests that there is no reduction in the severity of Omicron compared to Delta even for those who have finished the primary vaccination course, indicating that it is no longer mild. Omicron is not a harmless infection and can cause serious illnesses: the more infections there are, the more people will end up in hospital for this. to reduce the spread of the virus the booster is the best strategy“.
December 23, 2021 (change December 23, 2021 | 15:42)
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