May 28, 2022

Can you get Covid every three months? How and why we are reinfected

It is possible to resume Covid by becoming infected with the Omicron sub-variants. due to the characteristic of the virus that has chosen to evolve towards an increasingly marked ability to infect

Taking the rare but possible Covid two (or more times): statistically the reinfections officers are monitored by the Istituto Superiore di Sanit (Iss) which automatically considers reinfections cases of people who have returned positive 90 days after the first diagnosis. According to the latest monitoring, published Friday in Italy, the percentage of reinfections out of the total reported cases is equal to 5.8%an increase compared to the previous week (the value of which was 5%).

The variants present in Italy

The formidable contagiousness of Omicron one of the variables on which the risk of reinfection depends (the fundamental). The others concern: which vaccine has been made, which booster, for how long, which variant has been infected with the first time, how the body reacts. In particular, each variant of concern reported so far has increased its intrinsic ability to infect and, therefore, to escape immunity previous.
According to the latest Italian survey (referring to May 3) BA.2 represents 93.83% among the Omicron and variants, 12 sequences attributable to BA.4 and 6 sequences attributable to BA.5 were detected, equal to 0.47% and 0.41% of the total Omicron sequences, respectively. The World Health Organization (WHO) has stated that infection with Omicron BA.1 provides strong protection against BA.2 infection, however recent reinfection cases have also been documented between BA.2 and BA.1 .

Let’s say that this virus shows us its evolutionary capacity and that of increasing its contagiousness – explains Fabrizio Pregliasco, virologist of the Milan State University -. Its instability is allowing it to evolve into new variants that facilitate the ability to know how to “escape” both from the immunity conferred by the disease and from that given by vaccination.

Has this ability of SARS-CoV-2 to reinfect always increased, so far, with the arrival of the new variants?

Yes, because there is a consistent difference expressed every time (from Alpha to Delta to Omicron) in the characteristics of the antigen, in particular of the Spike: this is something that worries us, the same thing that we live in the antigens of the flu: every year we update the vaccine and a proportion of people who have suffered the infection in the past become susceptible again. There is therefore the need to strengthen the immune defenses with updated vaccine boosters.

Does the loss of immunity leading to reinfection depend on both the time since the last contact with the virus and the vaccination (or cured) status of each?

Of course, and the modification of the virus antigen causes us to lose the ability to respond adequately.

While the flu can take its worst once a year, Covid can currently be caught every three months, right?

Yes, this is the consequence of the evolutionary advantage of the virus we have talked about. In this phase also linked to the large share of infected people circulating: with the flu we have reached a balance, the share of susceptible is not very high.

What is the identikit of the person who should expect reinfection, what characteristics can he have?

There is no certainty: they are not only the most fragile, those who have more frequent and more risky exposure opportunities, but I do not see other intrinsic characteristics predicting a greater probability of getting sick again.

However, does personal probability also depend on some external factors such as vaccination?

Surely those who are not vaccinated are at greater risk, or those who have been vaccinated for a long time, or those who have never got sick from Covid. The more “resistant” subject is infected-vaccinated, then there are some personal genetic characteristics still not fully known today (and we see this for many diseases, such as hepatitis C and HIV), linked to the capacity of the so-called response mobile phone, which make an individual difference.

Even with reinfection, is the risk of having serious consequences much lowered?

The evolutionary advantage of the virus is to go towards the greatest contagiousness and not towards the greatest lethality. it is exaggerated, however, to say that the virus has “cooled”: some data tell us that it has reduced by 1/3 compared to the previous pathogenicity of variants such as Delta, but the lower impact on the severity of the disease is mainly linked to the spread of vaccination.

There is a lot of talk about updating the vaccine in view of the autumn, would it solve the problem of the loss of effectiveness of vaccines after a few months?

No, unfortunately it will be like with the flu, that is, we should consider the need for periodic vaccination boosters (hopefully on an annual basis, also in terms of practicality). I imagine a vaccination campaign substantially comparable to that of the flu and a coexistence with the virus that will have to lead us to have a “reasonable” attitude in evaluating the behaviors to be taken, with an additional fundamental weapon being antiviral drugs.

What is the advice given the situation?

For people at risk I recommend the use of FFP2 masks and again pay attention to contacts; for subjects not at risk to evaluate attendance with any fragile subjects in order not to be spreaders of the disease. The trivial but important generic answer is to continue to have some attention in situations of gathering and above all responsibility in managing one’s own possible positivity.

For the fourth dose?

Right now the fourth dose is important for the frail, because, even if the vaccine is not up to date, what interests us is to activate the memory T cells, which, thanks to this exposure, make it easier to trigger the immune response in the near future. .

May 14, 2022 (change May 14, 2022 | 18:02)

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