Premise: no one knows the future and it is impossible to predict what will happen in the coming months and years, with Covid19 we have learned that reality is more and more complex than models and forecasts. In recent weeks we have been seeing an increase in Covid19 cases more or less everywhere, mainly due to Omicron and its sub-variants.
Omicron appeared earlier this year and proved its infectious potency, for example in the United States it is estimated that 60% of the population has been infected with Omicron.
Omicron and its sub-variants
Despite the very high contagiousness, Omicron and its sub-variants (BA.1 / 2/5 etc) seem to be intrinsically less pathogenic, therefore able to cause a less severe disease in patients who contract it. It is not easy to calculate the pathogenicity of a variant, especially now that it is spreading in a largely vaccinated or cured population. In fact, we know that vaccines and healings (the latter to a qualitatively lesser extent) protect very well from the more serious manifestations of Covid19.
Omicron in addition to being extremely infectious is also able to evade the previous immunity and in fact millions of vaccinated and / or cured subjects have been re-infected. Re-infections in most cases are mild or comparable to initial infections.
Why do we get reinfected but don’t get seriously ill?
But then why do we get reinfected with Omicron but don’t get seriously ill? The answer lies in the immune system. Omicron has developed several mutations capable of bypassing the humoral immune response, i.e. that supported by neutralizing antibodies. Neutralizing antibodies are those that prevent infections, that is, they prevent us from infecting ourselves with Sars-CoV2.
Mutations accumulated by Omicron make it able to escape from neutralizing antibodies developed by vaccine or from healing but fortunately they do not escape from T lymphocytes. T lymphocytes that are part of the cell-mediated immune response, recognize different portions of Sars-CoV2 and this allows him to protect us from severe disease.
So we can potentially get infected with multiple versions of Omicron but disease protection should be provided by either vaccine or healing developed T cells.
It remains true that the more the variants are similar to each other, the more the antibodies produced will be protective against them, for example a subject cured of Delta can easily become infected with Omicron BA.5 while a subject cured of Omicron BA.2 is unlikely to get infected. with BA.5 (although it is possible).
The role of hybrid immunity
Hybrid immunity, i.e. that generated by vaccination plus infection to date, remains the most powerful in avoiding future infections, i.e. the chances of re-infection of a subject with hybrid immunity are lower than a subject only vaccinated, only cured or neither vaccinated nor cured. Obviously, it is in no way recommended to voluntarily become infected with Sars-CoV2, because even vaccinated / cured subjects risk serious consequences or long covid.
That hybrid immunity protects against infection can also be seen from English data, in fact about 84% of the British population is cured of Covid but today only 30% of registered infections are re-infections, this means that most of infections today (70%) occur in the naïve population (immunologically virgin) which represents only 16%.
In recent weeks, new sub-variants of Omicron are emerging and it seems that contagiousness is always increasing while little is known about the pathogenicity (difficult to calculate for the reasons illustrated above) but is this information on the individual variants important for us citizens?
While governments, researchers and public health managers must be constantly updated on the variants and their evolution, probably for citizens all this information is not useful, it only creates confusion.
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We citizens must focus on a few very clear points:
- The vaccine protects against severe disease and death, elderly and frail subjects may need multiple doses (fourth dose). The protection conferred by the vaccine is not infinite and specific recalls must be made for the various population groups
- We must avoid infection with several tools: indoor masks, positive ventilation and insulation. Obviously we cannot think of living in isolation in a bubble but we must try to mitigate the risks.
What can we expect for the future?
Keeping in mind the premise made at the beginning, we can say that to date there has not yet been a variant capable of completely evading the immune response. The immune system of most of humanity is no longer naive towards Sars-CoV2: most of us have at least once encountered the virus or part of it through the vaccine.
The creation of a global immune memory will increasingly reduce the impact of the virus which will be less and less able to create severe disease and deaths. For Sars-CoV2 to truly become a cold or flu (today it clearly still isn’t) two things that are not mutually exclusive can happen:
- the creation of a pan-coronavirus sterilizing vaccine: this vaccine would prevent infection by drastically reducing the circulation of future variants of Sars-CoV2
- the appearance of mutations that make the virus much less pathogenic. The likelihood of this event is unknown at the moment.
While we wait for Covid19 to become a cold we try to avoid infections and try to reduce viral circulation as much as possible.
REF:
https://www.medrxiv.org/content/10.1101/2022.04.29.22274477v1
https://www.nejm.org/doi/full/10.1056/NEJMoa2203965
https://www.nature.com/articles/d41586-022-01730-y?utm_term=Autofeed&utm_campaign=nature&utm_medium=Social&utm_source=Twitter#Echobox=1656123519
https://www.nejm.org/doi/full/10.1056/nejmc2108120
https://www.nejm.org/doi/full/10.1056/NEJMoa2203965
https://www.mrc-bsu.cam.ac.uk/now-casting/nowcasting-and-forecasting-23rd-June-2022/
Aureliano Stingi, doctor in molecular biology works in the field of precision oncology. He collaborates with the World Health Organization in the battle against Covid19-themed fake news
Instagram: @Aureliano _Stingi