The rumor has circulated claiming that vaccination aggravates contamination by SARS-CoV-2 via facilitative antibodies. What are facilitative antibodies? Is it really possible that vaccination makes the infection worse? The answer is no and here is why.
The vaccines aim to have our organization manufacture antibody neutralizers, i.e. antibody able to prevent the virus to spread in the body. In rare cases, antibodies may act as facilitators of infection rather than neutralizing them. There are two mechanisms that can cause an antibody to become facilitator.
Two facilitating mechanisms
The first known mechanism is the following. Facilitating antibodies are the same as neutralizing antibodies; they are produced by lymphocytes B of immune system. When they encounter the virus, they cling to it through the protein Spike, in the case of the coronavirus. As a reminder, the Spike protein is the surface protein of the virus which allows it to invade human cells.
Immune cells, macrophages, are then recruited to destroy the virus attached to the antibody. Normally, the antibody then becomes attached to both the macrophage and the virus. The macrophage will then digest the virus/antibody combination. This is when the antibody can become a facilitator. Instead of remaining anchored to the virus via spike protein, the bond may break. The virus is then released and, with its spike protein free, it infects the macrophage to replicate there.
What are the situations where an antibody can become a facilitator in this way? When a person is first infected with one variant of a virus and then a second time with another variant of the same virus with a slightly different surface protein, the binding between the antibody and the virus may be more fragile.
The second known mechanism is the following. When antibodies bind to circulating viruses, it causes an influx of immune cells. This influx can sometimes be disproportionate and lead to chain reaction immune cells. It follows a strong inflammation, deleterious for the body.
What about the Covid-19 vaccine?
The production offacilitating antibodies after one vaccination has unfortunately already happened. Here are some examples:
Cases have been described in the Philippines with the vaccine against the dengue (Dengvaxia) produced by Sanofi-Pasteur containing a virus attenuated. the dengue virus has five different variants. It was observed that freshly vaccinated children were infected with the virus and had a severe form of the disease. In December 2017, this vaccine was withdrawn from the market.
Cases of measles particularly severe have been reported after the injection of certain vaccines; these used an inactivated version of the measles virus. These vaccines are no longer on the market. The vaccines against measles currently in use contain a live version of the virus.
Regarding Covid-19, cases are suspected. One chinese item relates several potential cases, identified thanks to the serum convalescent patients. One other article describes the case of a 25-year-old American vaccinated and infected twice with two different variants. The second contamination was more severe than the first, suggesting the presence of facilitative antibodies or a more virulent variant in the latter infection. While these two articles cite potential cases, they are not evidence that vaccination against Covid-19 worsens contamination.
This phenomenon of facilitation is well known to the scientific community. Currently available vaccines are designed to minimize this risk. No cases have been scientifically found with the virus SARS-CoV-2.
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