All you need to know about the booster doses for corona – covid-19 vaccinations


When do people who have been fully vaccinated need booster doses of corona vaccines, and how are these additional doses effective in dealing with new strains of the virus, and can the type of vaccine be changed? All are questions that scientists seek to know.

The New York Times has tried to answer some of these questions and says that although many scientists suggest that the immunity provided by the “Pfizer”, “Johnson & Johnson” and “Moderna” vaccines can last for at least a year, no one knows for sure. It is also unclear whether emerging strains of coronavirus will change our vaccination needs.

And the US National Institutes of Health recently announced that it has started a new clinical trial on people who have been fully vaccinated with any of the authorized vaccines to see whether a booster dose of the “Moderna” vaccine will increase the amount of antibodies and extend the protection against infection with the virus they have, according to “Channel Free”.

Immunity varies with disease

Why should we get a flu shot every year, the report asks. But two measles injections during childhood could protect us for life?

The effect of different pathogens on the immune system works in different ways, and for some diseases, such as measles, a person’s illness once leads to lifelong protection from it, but for other pathogens, our immune defenses diminish over time.

The virus may mutate sometimes, creating the need for boosters to produce new defenses, which is the case for influenza viruses that are constantly mutating to the point that they require a new vaccine every year.

As for Corona vaccines, “we can’t be sure yet, because people started vaccinating in large numbers only a few months ago.”

“Even in experiments, we don’t know the immune response after a year,” says Dr. Kirsten Lake, a vaccine expert at the University of Maryland School of Medicine.

But current indications are encouraging. In vaccine trials, researchers have observed that antibody levels diminish gradually, which means that protection may last for a long time, and people who were previously infected and then received the vaccine may enjoy longer protection.

Dr. Edward Bilongia, a physician and epidemiologist at the Marshfield Clinic Research Institute, predicted that immunity would last “for years against the original strain”. The newspaper says that if this is proven, we may not need Corona boosters for years.

The effectiveness of vaccines varies according to the technology used

Scientists have found that the effectiveness of vaccines varies according to the technology used, and vaccines that rely on “mRNA” technology such as “Pfizer”, “Moderna” and “Johnson & Johnson” have greater effectiveness, while vaccines that rely on inactivated viruses, such as the Chinese “Sinopharma” vaccine. They are somewhat less effective.

Scott Hensley, an immunologist at the University of Pennsylvania, has found similar results in his own research on mice receiving different types of flu vaccines, some made with RNA-based technology and others inactivated viruses.

Studies indicate that the effectiveness of the “Sinopharma” vaccine is 78 percent. Because of this, the UAE and Bahrain are currently giving boosters to people who have received this vaccine.

According to Reuters, the UAE is now recording about twice as many cases of corona infection, compared to the numbers it was monitoring seven months ago.

A study published in the “Jama” medical journal had said that the Chinese vaccine is 78.1 percent effective against symptoms of corona infection.

When do we know we need to get booster shots?

Scientists are looking for biomarkers that can detect when our immunity has become insufficient, and thus establish a “threshold” at which we can tell when it’s time to take additional doses.

Boosters for new breeds
We may need boosters to prevent infection with the new strains, but that’s not clear yet. Indeed, the emergence of strains in recent months has accelerated the search for enhancers.

Some strains have mutations that have led to their rapid spread, and others carry mutations that may reduce the effectiveness of some vaccines. At this point there is not much information about how the current vaccines work against the different strains.

But last month, a study found that the “Pfizer” vaccine was 95% effective against the original version of the Corona virus, but a strain called “Alpha” that was first discovered in Britain reduced the effectiveness to 89.5 percent. For a strain from South Africa called “Beta”, the effectiveness of the vaccine was reduced to 75 percent, but the vaccine was 100 percent effective against the two strains in preventing severe, critical or fatal diseases.

However, just because new strains are able to evade existing vaccines does not mean that it will become a widespread problem. Beta, for example, has remained rare in countries with strong vaccine programmes, such as Israel, Britain and the United States.

But development still has “a lot of room to play” and scientists do not rule out the possibility of new strains emerging in the coming months that spread rapidly and are resistant to vaccines.

Specific booster for a particular strain?

Scientists do not yet know whether we will need special boosters for certain strains, but it may happen, and Pfizer has already started an experiment on this issue, and through it, some volunteers who have already received two doses of the vaccine will receive a third dose as a booster, and they will be Give other volunteers a booster designed to protect against the beta strain.

Switching the type of vaccine

Perhaps people will be able to get a booster dose of a different vaccine than the original type. And plenty of research on other diseases suggests that switching vaccines can strengthen boosters.

Researchers are recruiting volunteers who have been fully vaccinated with any of the three vaccines authorized in the United States against Corona, to all receive a booster dose of “Moderna” only, provided that the strength of their immune response is monitored after that.



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