The top US public health official has given the green light to use "mix and match" booster doses to increase antibodies to the novel coronavirus.

Under the decision of the Director of the "Centers for Disease Control and Prevention" Rochelle Walinsky, from now on, eligible people can receive any of the three booster doses available regardless of which type of vaccine they get first.

The Food and Drug Administration has authorized the additional injections, and the CDC has also updated its guidance for these doses.

The boosters are especially important for the elderly and those with conditions that put them at risk of severe infection, especially with the approach of winter and the holiday season.

Here's what you need to know about these mixed and matched boosters:

What does "mix and match" vaccines mean?

A patient who received a second or third dose of a different type than the previous dose is said to have received “mixed and identical” vaccines, and these doses are also described as “heterogeneous.”

As an example, say someone had a mixed dose if they received a dose of Johnson & Johnson in the spring and got a booster dose of Moderna this fall.

It also includes in the same framework a person who received two initial doses of the Moderna vaccine, but chose a booster dose of Pfizer, for example.

What are the latest CDC recommendations for booster doses, mixing, and matching?

Rochelle Walinsky has authorized the Johnson & Johnson booster injection for people over the age of 18 to be given to them at least two months after their first vaccination.

The move comes after data showed that the initial single-dose regimen offers less protection than the two-dose regimen of Moderna and Pfizer-BioNTech.

It also allowed the administration of a dose of the Moderna vaccine as a booster dose to anyone over 65 years of age who suffers from high-risk conditions, or to front-line workers who may be exposed to infection in their workplace.

Eligibles can receive this booster after 6 months or more of their initial two-dose regimen of Moderna (Pfizer booster approved last September).

Experts say there is no evidence that receiving two different vaccines against the Corona virus causes any harm (Reuters)

Is mixing and matching safe?

So far, experts say that there is no evidence that receiving two different vaccines against the Corona virus causes any harm, and a recent study that tracked people who received booster doses by mixing and matching, and presented last Friday to the “Center for Disease Control”, did not indicate any negative incidents. dangerous related to mixing vaccines.

But experts also point out that data on mixed and matched vaccines is limited to a small number of people, compared with large studies that previously and separately demonstrated that this or that vaccine is safe and effective.

Why are officials considering the use of mixed and matched vaccines?

Allowing people to receive any booster vaccine can make it easier to find a booster dose and give health care providers more flexibility in providing vaccines to patients who previously received a different vaccine than the one they already have.

And any booster injection, even if it is similar to the first dose, can increase the number of antibodies that can fight the virus, and in some cases - as experts confirm - mixing vaccines may provide better protection, as early data showed that following the first dose of Johnson & Johnson with the Pfizer vaccine. Or Moderna provide much higher levels of antibodies.

How does someone decide which fortified dose is best for them?

Health officials say that people who are eligible for a fortified dose can consider the benefits and risks of each product, and talk to their healthcare provider about the most appropriate one.

These officials and doctors have repeatedly stressed that the benefits of vaccinations against the Corona virus far outweigh their potential risks.

The Moderna and Pfizer vaccines are generally associated with a rare risk of developing inflammatory heart diseases, such as myocarditis, where males under 30 are more likely to develop, but a follow-up study of heart problems presented to CDC advisors last week indicated that these cases are generally mild, and that Symptoms are treated immediately.

As for the Johnson & Johnson booster vaccine, its potential risks include a rare and dangerous type of blood clot known as thrombosis with thrombocytopenia syndrome.

Another potential risk is a rare side effect called Guillain-Barré syndrome, a disorder in which the immune system damages nerve cells, resulting in muscle weakness and sometimes paralysis.

The people most at risk of developing this syndrome are men between the ages of 50 and 64. According to the Centers for Disease Control and Prevention, most recover completely, while some have permanent nerve damage.

Experts differ on whether Covid infection provides enough lasting immunity to forgo a booster dose (Reuters)

Can someone who is immunocompromised who has received an extra dose get a fourth dose?

Yes, it can, according to the CDC, which also confirms that people with moderately or severely weakened immunity who have already received a third dose of the Pfizer-Biontech or Moderna vaccine, can get a fourth injection 6 months or more after the last vaccination. .

They can also receive a booster dose of any of the 3 vaccines for a total of 4 doses.

I am fully vaccinated but I have a critical infection.. Do I need a booster?

Experts still differ on whether the Covid infection provides enough permanent immunity to forgo a booster dose, and what is certain is that the immune system that must fight the virus produces antibodies, but these antibodies may fade over time just as those produced by vaccines do.

However, some experts believe that people who contract the virus and are fully vaccinated also eventually develop the strongest immunity, whether they become infected before or after vaccination.

While others believe that obtaining a booster dose even after fully recovering from Covid-19 disease will not harm, including William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center in Nashville, who confirms that “there is no evidence that there will be harm” as a result of receiving subsidized doses. .

Why are boosters effective?

Boosters help train the body to fully respond to pathogens. “A single booster dose helps the body build durable memory cells that are able to fight pathogens for periods of time,” says Costi Siveri, director of epidemiology at Virginia Health University.

He believes that under the previous mutants of the Corona virus, the vaccine antibodies from the initial doses were good enough to protect against infection with the virus for up to 6 months, but the more contagious delta variant confirmed the need for booster doses so that the body could continue to fight against a dangerous disease and avoid entry. the hospital.

Tom Russo, professor and chair of the Department of Infectious Diseases at Buffalo Jacobs University of Medicine and Biomedical Sciences, confirms that scientists use their knowledge of other viruses and apply it to the Corona virus, but they are still at the steeper end of the learning curve.

"We knew we needed a tetanus shot every 10 years, but there was a point where we didn't know it... We are constantly learning with Covid disease," he adds.