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Covid, infected despite the vaccine: what does it mean?

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Covid, infected despite the vaccine: what does it mean?

Between winter and spring 2022, thousands of vaccinated people were infected with the Omicron variant of SARS-CoV2. Why have so many people been infected despite the vaccine? Does infection in a vaccinated person provide additional protection for the future?

Vaccines against the disease

The mRNA vaccines used in Europe have proved extremely effective in preventing the death and hospitalization of vaccinated people, let us remember that this was the primary objective: to limit deaths and decrease hospital pressure. Furthermore, the anti Covid19 vaccines are effective in avoiding the symptoms of the disease in the first months after inoculation, in fact it is rare to get Covid19 in the first 3 months post vaccination. Finally, to an even lesser extent, the anti Covid19 vaccines also reduce the risk of infection but for an even shorter period.

The Omicron variant that emerged at the end of 2021 is characterized by a series of mutations that make it extremely contagious on the one hand and also able to circumvent the immune response on the other.

This ability to partially evade the immune system has made possible the numerous infections in fully vaccinated subjects that we have observed in recent months.

Put simply, our immune system was initially fooled by Omicron, which managed to enter our body (infection) but fortunately failed to do damage (disease). This is because our immune system is made up of different levels of security and therefore a vaccinated person can become infected with a mutated variant but very rarely will experience serious illness or worse death.

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Why does the vaccine not protect against infection for a long time?

We have learned that the first line of defense against a respiratory virus such as Sars-CoV2 is found in the mucous membranes of the upper airways: nose, mouth, pharynx etc. In these mucous membranes there is a special population of antibodies called IgA.

IgA are specialized in neutralizing respiratory viruses upon entry and are precisely produced in the mucous membranes. MRNA vaccines are able to stimulate the production of this special class of antibodies but unfortunately in limited quantities. It has been observed that individuals who produce the most IgA following vaccination will also be the most protected from future reinfection. The stimulation of IgA is the basis of the spray vaccine we have discussed in the past, in theory this vaccine should confer the so-called ‘sterilizing immunity’.

A spray vaccine against Covid

by Aureliano Stingi

December 20, 2021

I got vaccinated against Covid19 but I got infected anyway, what happens?

Despite the vaccine, Sars-CoV2 infection is never pleasant or recommended, but infection with Omicron could be ‘good news’.

In fact, a recent study compared the different types of immunity: recovery, vaccine (1/2/3 doses) and hybrid (vaccine + infection). The results seem to indicate that the maximum protection against infection is conferred by hybrid immunity: that is, that immunity triggered by a Sars-CoV2 infection followed or preceded by a complete vaccination course.

These data therefore confirm two things: first, even the healed subjects should complete the vaccination cycle and second probably the natural infection contributes to producing the IgA antibodies that prevent contagion.

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Will people with hybrid immunity be protected forever from Covid19?

Unfortunately, we know that Sars-CoV2 changes a lot and in recent weeks some sub-variants of Omicron are emerging which appear to be able to re-infect even those who have been infected with Omicron this winter, even if vaccinated.

Reinfections tend to be mild in most of the population vaccinated or in contact with previous sub-variants of Omicron, but can be dangerous in frail, elderly and immunosuppressed subjects. For these reasons, a second booster dose (fourth dose) is recommended for these categories. Furthermore, despite the protection conferred by hybrid immunity, it is always not recommended to expose yourself (intentionally or accidentally) to the virus, which is why a mask is recommended in particularly crowded and poorly ventilated contexts.

Finally, there are currently several phase 3 spray vaccines. If approved, a combination of spray vaccines + classical intramuscular vaccines could confer sterilizing immunity in a totally safe and controlled manner, replacing the hybrid immunity we have now achieved with the vaccine + infection combination. .

This article was written with the collaboration of Dr. Massimo Fantini, Senior Scientist specializing in tumor immunotherapy. It is understood that the opinions contained therein are entirely personal.

TAKE HOME MESSAGE

  1. Vaccines protect against death, hospitalization and symptomatic illness but to a lesser extent against infection
  2. Sars-CoV2 infection is prevented by special antibodies produced in the mucous membranes called IgA
  3. Hybrid immunity conferred by vaccination plus infection is the one that provides the best protection from future infections

REF:

https://www.nejm.org/doi/full/10.1056/NEJMoa2118691

https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(21)00648-4/fulltext

https://www.nature.com/articles/s41385-022-00511-0

https://www.medrxiv.org/content/10.1101/2022.03.22.22272745v1.full.pdf

Aureliano Stingi, doctor in molecular biology works in the field of precision oncology. He collaborates with the World Health Organization in the battle against Covid19-themed fake news

Twitter: @AurelianoStingi Instagram: Aureliano _Stingi

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