Good news for the healed, which in Italy are over 3 million: a large study carried out on health personnel (therefore at risk) in Great Britain confirmed that the risk of resuming Covid is very low, at least up to 7 months after.
Previously it was estimated at 5 months
The study, published April 9 in the scientific journal The Lancet, aimed to establish whether reinfection was symptomatic or asymptomatic, whether reinfected individuals were infectious for others, and the duration of immunity from the first infection. More than 90% of individuals infected with SARS-CoV-2 develop antibodies approximately 1 week after the onset of symptoms and although the exact duration of immunity conferred by natural infection is still unknown, in various research and subsequent updates (follow up ) has come to establish that the titles of neutralizing antibodies against the spike protein SARS-CoV-2 were still detectable for at least 5 months after primary infection. This English study shifts the bar a little further forward in time.
I study
The staff examined consisted of health care workers, support staff and administrative staff of National Health Service (NHS) of the United Kingdom, subjects particularly exposed to the presence of SARS-CoV-2, enrolled for a total of 25,661 participants. 8,278 people (32.3%) were assigned to the positive cohort, representing those who had a previous Covid infection and 17,383 (67.7%) were assigned to the negative cohort, people who have never been positive for coronavirus. All participants underwent for 12 months in molecular buffer every 2 weeks and serological tests (antibody tests) every 4 weeks. The median duration of follow-up per participant was 275 days for the positive cohort and 195 days for the negative cohort. By 11 January 2021, 1,859 new infections were detected in the study population: 1,704 primary infections in the negative cohort and 155 reinfections in the positive cohort.
90% protection
Of the 155 reinfections, 78 (50.3%) were symptomatic, 50 (32.3%) with typical Covid symptoms. The median range between primary infection and reinfection episode for the 47 cases with a positive PCR test from their primary episode been 201 days (with a range of 95–297 days). For the 99 cases who provided a history of Covid symptoms and not a swab to estimate the date of their primary infection, the median interval between primary infection and reinfection was 241 days (range 90–345). The final calculation, skimmed by possible errors and indeterminable cases, showed that previous infection reduced the incidence of infection by at least 90% and, even including those not fully confirmed among the reinfections, the previous Covid infection reduced the incidence of reinfections by at least 84%.
Protection also against the English variant
We believe this is it the least likely effect. We have identified and investigated more potential reinfections than reported in the global literature to date, the researchers write, adding: After 7 months of follow-up, this large observational study showed that previous SARS-CoV-2 infection protects most people from reinfection for an average of 7 months and conclude: In this analysis we also demonstrated that immunity from previous infection was protective against the English variant (B.1.1.7), which in the months of the study expanded and became prevalent in the UK.
One dose of vaccine is enough
The study confirms that a previous infection (even if asymptomatic) protects the body for months because the immune system recognizes the virus. This evidence makes the proposal even more valid vaccinate the recovered with a single dose: the first infection serves as a trigger for the immune system, the dose of vaccine is enough to enhance this response, even in those who (perhaps elderly) have developed fewer defenses.
The confirmation of good protection also justifies the idea of a pass to be extended also to the healed, obviously with characteristics to be defined especially with regard to the months passed since the first infection and the documents (tests) to be shown to certify the recovery.
April 19, 2021 (change April 19, 2021 | 07:03)
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