Why are Covid reinfections so frequent?
Vaccines certainly help but how is it possible that Covid reinfections happen even after a short time? A new study explains why and thinks the solution is in spray vaccines. All the details
Covid reinfections are now, so to speak, normality and above all it has been observed that they can also happen in a very short time and not necessarily after 4-6 months, which was the period indicated for immunity left by the disease.
But why, despite the antibodies produced by the infection or by the vaccine, are Covid reinfections so frequent?
ISS DATA
From 24 August 2021 to 14 December 2022, the latest update from the Istituto Superiore di Sanità (ISS) on the impact of the pandemic and the effectiveness of vaccines, 1,612,217 cases of reinfection were reported, equal to 7.9% of the total of cases notified in the same period.
In the last week, the percentage of reinfections (20.9%) decreased slightly compared to the previous week (21.3% last week, data with longer consolidation times than other information).
WHY COULD COVID REINFECTIONS BE FREQUENT?
The problem of reinfections from Covid would lurk in the nose. This is what is supported by an Imperial College London study published in eBioMedicine , according to which the antibodies produced in the nose have too short a life.
The barrier inside the nose is in fact the first line of defense against infection because it blocks the virus as soon as it tries to enter. If the antibodies present in the blood continue to guarantee high protection against serious disease even 9 months after vaccination, those in the nose disappear much sooner. Which is why spray vaccines could be of great help.
I STUDY
The follow-up study involved 446 adults who had been hospitalized for Covid between February 2020 and March 2021 and, therefore, before the spread of Omicron.
Plasma and nasosorption samples were taken on admission, six months after infection and one year later. The level of antibodies in the participants' noses was then measured at various points in time and compared with the duration of that detected in the blood.
THE RESULTS
In the vaccinated people, the experts noted an increase in the levels of all antibodies, both in the nose and in the blood, however, the nasal ones had increased slightly and remained detectable for a short time.
The antibodies present in the blood, however, continued to be detectable even a year after the infection, caused by the original strain, Delta or Omicron.
This means that vaccination remains the most effective weapon against serious disease , but it would be equally useful to have spray vaccines available that can nip the infection in the bud. “While blood antibodies help protect against disease, nasal antibodies can prevent infection altogether. This may be an important factor behind repeat infections,” the authors commented.
WHERE ARE WE WITH SPRAY VACCINES
Although there are several under study, currently only India and China have produced and licensed anti-Covid spray vaccines. Bharat Biotech's nasal version is available in India, but it has not yet disclosed the results of its studies. China, overwhelmed by a wave of infections , with its Convidecia Air claims that one puff is enough to get good protection.
However, as Mike Diamond, a virologist and immunologist at Washington University in St. Louis (who helped develop the spray vaccine used in India), pointed out in The Atlantic , "nothing has been published, no data has been made available." and therefore the doubt remains on the effectiveness.
Also, when it comes to making a mucosal vaccine for a respiratory virus, "we don't have a model to follow," explained Deepta Bhattacharya, an immunologist at the University of Arizona, and that's because there is currently only one mucosal vaccine to fight a pathogen. that enters through the nose. It's called FluMist and it's a spray composed of weakened flu viruses, quite protective in children but much less powerful in adults.
This is a machine translation from Italian language of a post published on Start Magazine at the URL https://www.startmag.it/sanita/perche-le-reinfezioni-da-covid-sono-cosi-frequenti/ on Thu, 22 Dec 2022 09:52:00 +0000.