Cantabria shows that the Omicron variety is easier to contaminate than the delta and analyzes its cause

2022/01/25 Galarraga Aiestaran, Ana - Elhuyar Zientzia Iturria: Elhuyar aldizkaria

Ed. Manuel Álvarez/Pixabay

Researchers from the Cantabria Public have calculated the secondary health rate of the omicron variant, that is, the number of cases that appear in close contacts of an infected person (SAR), transmission, incubation time and interval, comparing them with that of the delta variant. Thus, it has been observed that the transmission of omicron is higher (the SAR of omicrons is 39% and that of delta 26%), with a higher propensity for asymptomatic infection. it has been concluded that isolation time can be reduced.

Adrian Hugo Aginagalde Llorente is one of the researchers and has stressed that the greatest risk of infection with omicrons occurs before symptoms appear. In this sense, the monitoring and cutting of the contamination chains is complicated, as the infected person is not isolated in time and close contacts are also late.

Along with this, the infected take less time to become infected: “We have seen that five days after symptoms, the risk of transmission of the virus decreases considerably. So on average, on the sixth day, I could go out on the street. However, the protocol states that the isolation must be seven days,” said Aginagalde. That's right: to reduce, you can do it based on scientific evidence.

Another conclusion is that, once infected, vaccinees have a risk equivalent to those not vaccinated for transmission of the virus. “In other words, we have not seen the inserts have less transmission. In this sense, it is indifferent to be inserted or not”.

All these factors, that is, they are very asymptomatic, that the greatest risk of infection occurs before the symptoms appear and that vaccinees contaminate as much as unvaccinated ones, have contributed to the omicron variety expanding so easily. “There may be biological reasons to explain such a rapid expansion. For example, it has been confirmed that it replicates more in the upper respiratory tract than in the lungs, which can also facilitate transmission. But other factors have a direct influence, as they hinder anticipation, for example, if isolated in time, infected or exacerbating non-pharmacological measures, in case of suspicion of close contact”.

In fact, research has shown that half of the infections with omicron occurred before symptoms appeared. This means that the effectiveness of non-pharmaceutical measures to detect symptomatic cases (e.g. contact tracing, rapid testing and isolation) is greatly reduced unless other measures are taken to ensure distance and avoid excessive concentration of people.

Finally, Aginagalde has highlighted the value of this type of research, since it allows decision-making in scientific data.


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