Who recovered from Covid risks taking it back? And how much? The share of those who fall ill after being healed is increasing, but T cells remain active against the new variant and presumably protect against severe disease
How likely is a person recovered from Covid to get reinfected today?
The risk exists and is not negligible. According to the latest report from the Higher Institute of Health (Iss), reinfections from 24 August to 9 January were 2.7% of cases (over 108 thousand) and in the last week they increased to 3.2%, compared to at around 1% recorded from October to early December (Omicron was isolated on 11 November). Data collected by Imperial College London show that, with the new variant, contagion after healing is 5 times more frequent than with Delta. Therefore, the protection offered by a previous infection would have been reduced, against Omicron, to 19% (compared to 85% calculated with other variants).
Who risks the most?
The unvaccinated and health workers: 21,000 cases of reinfection in non-immunized people between mid-December and mid-January, according to the ISS report, 2,800 cases among those vaccinated with at least one dose at the time of first diagnosis and 65,000 among those who received the vaccine after the first infection. In the category of health workers, reinfections were over 4,000 in one month, compared to 37,000 first diagnoses (in the rest of the population the ISS calculated 72,000 reinfections compared to 2 million first diagnoses). Looking at the age groups, more than 20-39 year olds got sick again (39% of total reinfections), followed by 40-59 year olds (34%). Geographically, 74% of the second (or third) infections occurred in Northern Italy.
How much time can elapse between the first and second infection?
The Ministry of Health defines reinfection as the person who contracts Sars-Cov-2 at least 90 days after the previous illness, or less than 90 days but with a different viral strain, documented by genotyping.
Does anyone who gets sick for the second or third time have milder symptoms?
We know that Omicron correlates with partial immune evasion, as far as infection is concerned. This means that those recovered and vaccinated are less protected from contagion. We have very solid data that show how the T cells, those of the immunological memory, remain active even against the new variant, avoiding severe forms of the disease – he explains Mario Clerici, full professor of Immunology at the University of Milan and scientific director of the Don Gnocchi Foundation -. This explains why today, despite the very high number of infections, the share of hospitalized patients, even in intensive care, does not reach alarming levels (in Italy there are about 20 thousand hospitalized, compared to 2 million and 700 thousand positive, ed).
Could those recovered from Omicron get infected with the same variant?
unlikely, because during an infection the body produces an immune response specifically directed against the responsible virus. We can therefore assume, except for very fragile or immunosuppressed subjects, that being infected several times with the same strain is very rare. We must consider that Delta and Omicron coexist right now – underlines Clerici -. The first may be decreasing, in percentage terms, but it has not disappeared. Being healed of either variant may not protect the other. Getting vaccinated is more important than ever, because it saves us from severe Covid.
January 22, 2022 (change January 23, 2022 | 10:53)
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