Those who fall ill with Covid and then recover, it is good that you do not let your guard down. Not only is the risk of reinfection, in fact, always around the corner. But as if that were not enough, Omicron and Delta are in fact two different viruses and therefore the immunities acquired after healing are not superimposable. “We are not sure that a previous infection with Delta will protect against Omicron. We do not have enough data to be able to affirm this – explains Francesco Menichetti, professor of infectious diseases at the University of Pisa, director of infectious diseases of the Pisa university hospital and president of Gisa (Italian antimicrobial stewardship group) – We know, however, that with full-cycle vaccines after three doses we have partial protection, especially from contagion. We also know that you can be reinfected, because Delta infections happen to people who are vaccinated and also to previously infected with Delta, Alpha or the Wuhan virus. Let us remember, therefore, that these viruses, in the case of infection, give an immunity that is relative and of short duration ».
Healing does not guarantee immunity
The idea that one should feel safe from a new contagion because one is already sick is therefore without foundation. «Immunity against Omicron – Menichetti reiterates – is different and is not protective against other more pathogenic coronaviruses, more capable of attacking the lower respiratory tract. Conversely, we have seen that those who have been previously infected can also become infected with Omicron. In any case, they are not superimposable. After all, Omicron has 32 mutations, therefore it presents a very significant change both in pathogenicity but also in immune response ».
Omicron a virus other than Delta
It is useless to hope to be able to run into a less dangerous variant. «It is still believed that the majority of those hospitalized with severe Covid in intensive care are from Delta infection. But we are not absolutely sure – specifies the infectious disease specialist – Nobody, in fact, tells us how many of the daily hospitalized patients in intensive care have been infected with Delta or Omicron. However, we have the feeling that Delta continues to supply the wards, while Omicron supplies home isolation. But, I repeat, not having a systematic English-style surveillance system, we make assumptions. Generally speaking, Omicron is a virus substantially different from Delta, and probably less pathogenic, unless it encounters particularly fragile or susceptible individuals ».
The Omicron-Delta Double Infection
If you get in the way of chance, it cannot be ruled out that you are even infected with both. “It is likely that it will happen – specifies Menichetti – in theory, coinfection could be possible, but it is more likely between flu and Covid”. Therefore, pay attention to the precautionary measures, which must always be respected even after recovery. «We are in a situation where Delta was circulating and now Omicron is coming overwhelmingly. The most probable scenario – explains the infectious disease specialist of the University of Pisa – is that one passes from Delta to Omicron and that therefore a subject who has had Delta is exposed to the new variant. On the other hand, it is unlikely that those who have now become infected with Omicron, which is the latest variant that is circulating, will then fall ill with the Delta. Omicron’s progression should in fact quickly exhaust the Delta tank ».
The importance of the third dose
But the temporal succession of infections with the two variants does not affect the development of the disease. «We know that in general Omicron gives milder forms – remarks Menichetti – but we do not know if it is due to the fact that the subject first had the Delta, or because it is itself less aggressive. Therefore, Omicron sic et simpliciter should not be considered a benign virus. We remember that if we have to contract Omicron it is better that it happens with complete vaccination protection with the three doses, because we would still be more protected from contagion and possibly from complicated and serious forms “.
Herd immunity
The mitigation behaviors of the spread of the infection therefore remain fundamental. “We still have too many unvaccinated – warns Menichetti – but we also have vaccines that do not absolutely protect against contagion. I therefore believe that it is very dangerous to feel safe for possible herd immunity. Recall that the most exposed are the unvaccinated, then those with a single dose, then those with two and finally with the three doses, which give the highest level of protection, over 80 percent, mainly against serious disease. requiring hospitalization. The prevention of contagion, on the other hand, remains imperfect ».
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