Home » Covid, what we know so far about the fourth dose

Covid, what we know so far about the fourth dose

by admin

After more than two years since the start of the pandemic, it is natural to start wondering what will happen next, how we will get out of this situation and, above all, when.

We have learned that making predictions is dangerous and almost always bankruptcy but, at the same time, reflecting on the future is necessary.

The point of the situation

We are currently facing the highly contagious but less lethal Omicron variant. About 90% of Italians received at least one dose of the vaccine, while 73.3% received the third dose by completing the vaccination cycle. Since January 2020 our immune system has encountered Sars-CoV2 several times, both by infection and by vaccine and thus an “immune memory” has been built in us: that is, our immune system has an idea of ​​this virus which , until two years ago it was completely new and unknown.

Ema’s position

The European Medicines Agency (Ema) expressed itself informally during a press conference regarding the hypothesis of a fourth dose to be administered indiscriminately to the entire population. The EMA does not consider a fourth dose so close in time to the third necessary or useful and this position has triggered the reactions of conspiracy theorists and skeptics. But let’s try to understand the position of the EMA.

We have learned that our immune system is an army made up of different departments that attack pathogens in different ways. The vaccine works like a mugshot by instructing members of the military to fight against a specific element of the enemy (in the case of Covid19 vaccines, the viral Spike protein).

See also  Cuban Man Exhumes Mother's Grave, Finds Another Person Buried Inside

Three doses are enough

Three doses of the vaccine are perfectly capable of stimulating a sufficient immune response consisting of neutralizing antibodies, cytotoxic T lymphocytes and memory B and T lymphocytes. Memory lymphocytes confer long-term protection and, if after the vaccine we were to come into contact with the virus, they would reactivate immediately to produce new antibodies and T lymphocytes in order to eradicate the virus in a short time.

Why, according to the EMA, might a fourth dose in the general healthy and immunocompetent population not be useful in the short term?

Premise: at the moment there are no data on a fourth close dose for the anti-Covid vaccine19, so the hypotheses expressed should be understood as such. This article addresses the potential risk of administering multiple doses over a short time horizon.

The immune system

Repeated and close stimulations with the same antigen (Spike protein) could in fact ‘numb’ our immune system. For example, stimulation of T lymphocytes for the fourth time in a few months with the same antigen presented to the body in the same way and through the same type of vaccine in healthy and immunocompetent subjects could induce the phenomenon of ‘exhaustion’, in which the lymphocytes appear exhausted and show reduced activity in fighting the virus as explained by Massimo Fantini, Senior Scientist specializing in tumor immunotherapy.

The phenomenon ofexhaustion of T lymphocytes occurs naturally in the case of chronic viral infections or in the case of cancer. In the case of chronic viral infections, the persistent stimulation of our immune system with antigens belonging to the same pathogen that fails to be eradicated causes the reduction of T cell activity and determines their exhaustion.

See also  This deadline applies to filing your tax return in 2024

As a result, our weakened immune systems are no longer able to respond optimally to infection.

The risk of exhaustion

The risk of exhaustion too many close doses with the same vaccine could occur for the part of the population in which the immune system is perfectly functioning and without pathologies. We have learned that the immune system deteriorates and loses responsiveness as we age. The elderly, frail and immunosuppressed, therefore, may still need a fourth booster dose precisely because their immune system is less reactive to the vaccine stimulus.

What to do?

At this point it is necessary to segment the population and make decisions accordingly:

frail, immunosuppressed and elderly individuals may need a fourth dose to stimulate the immune system a few months after the third dose is administered. For the rest of the population, however, for whom a fourth dose a few months after the third would not be needed, one could think of using the flu vaccine scheme by administering one dose per year in autumn, updated on the prevailing variant.

What to do with the new variants?

But what to do in case of new variants? Sars-CoV2 will certainly change again and, to face future mutations, several laboratories around the world are developing a pan-coronavirus vaccine that should also cover these future variants.

Will a sterilizing vaccine arrive? For the moment it is difficult to answer, but several laboratories are working to create a spray vaccine capable of stimulating the production of IgA in the mucosa that act as a barrier to the virus. The most advanced at the moment are the Indian BBV154 vaccine and the Cuban Mambisa vaccine.

You may also like

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.

This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More

Privacy & Cookies Policy