- Writing
- BBC News World
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Many countries are rapidly implementing their Covid-19 booster vaccination programs.
The decision was prompted by concerns regarding the weakening of immunity conferred by the initial vaccines, which were developed to combat the initial form of the coronavirus, which appeared two years ago.
But there are also new fears regarding the risks associated with the highly mutated Omicron variant that has spread around the world.
To read especially on BBC Africa:
Studies have shown that two doses of vaccines do not provide sufficient protection once morest an Omicron infection, although they have reduced the risk of serious illness and hospitalization.
Here’s what booster shots are and why they’re needed to maintain immunity once morest the coronavirus.
What is a booster vaccine?
The Covid booster vaccine is a third (or second in the case of Janssen/Johnson & Johnson) dose of the vaccine that was originally given to prevent infection with the coronavirus.
Booster doses were approved by health authorities in many countries following it became apparent that the protection provided by two doses of the original vaccines began to wear off following a few months.
Booster doses are designed to help people maintain their level of immunity for longer.
Two studies published on January 21 by the US Centers for Disease Control and Prevention (CDC) show that the effectiveness of certain vaccines in preventing serious illness and hospitalization due to Omicron infection fell to only 57% in people who received a second dose of their vaccine six months previously.
The booster dose restored this protection to a level of 90%, the study indicates.
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2. Why do I need a third dose of vaccine if I already have two?
The original Covid vaccines have been shown to prevent serious illness, hospitalizations and deaths.
However, the emergence of the Omicron has changed the landscape of the pandemic, as Dr Ignacio Molina Pineda de las Infantas, a professor of immunology at the University of Granada’s Biomedical Research Center, explains to BBC Mundo. Spain.
“With two doses, the protection we obtained was optimal for all the variants that had appeared so far, including the Delta variant,” he says.
“But you have to understand that the Omicron variant is almost a different disease, that is, it has so many variations from the original virus that it behaves very differently.
“Given that we are dealing with a very different variant of the original virus and that we are vaccinating with vaccines designed for the original virus, we have found that giving two doses is not enough to confer adequate protection,” says- he.
3. Is the Omicron booster vaccine effective?
The studies published Jan. 21 in the US CDC’s Morbidity and Mortality Report are the most comprehensive evaluations to date of booster vaccine effectiveness once morest Omicron.
The researchers analyzed tens of thousands of Covid cases, hospitalizations and deaths, as well as emergency room visits in several US states.
Studies show that the booster dose is 90% effective in preventing Omicron-related hospitalizations and deaths, especially in people over the age of 50.
Also, a lower percentage of Covid cases and deaths were seen in people who received a booster dose than in those who received only two doses.
Another CDC study, involving more than 70,000 people and published in the Journal of the American Medical Association (JAMA), showed that the booster dose provides better protection once morest Covid infection than just two doses. or none.
However, the data show that both the original vaccine and the booster vaccine offer less overall protection once morest the Omicron variant than once morest the Delta variant.
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4. Do I need a booster dose if I have Covid?
As immunology professor Ignacio Molina explains, “it all depends on the variant you were infected with”.
“If you have been infected with one of the original variants (like Alpha or Delta), the risk of re-infection is obviously very high, once more because Omicron is a completely different or very different variant from the previous ones”.
“I think that following a while it makes sense to vaccinate the person who has not been infected with Covid once more with a booster dose,” explains the expert.
5. Can I receive a booster vaccine different from my initial vaccine?
Yes, different brands of vaccines can be mixed and matched.
Each country has authorized different vaccines and now each government authorizes its own booster vaccines as well.
In the United States, for example, the Food and Drug Administration (FDA) has given the green light to three booster vaccines: Pfizer, Moderna and Janssen/Johnson & Johnson (for some cases) and determined that it is safe to receive a booster from a different brand than the initial dose.
In the UK, authorities have approved the Pfizer and Moderna booster shots, meaning many people originally vaccinated with the Oxford/Astra Zeneca vaccine are getting a different brand booster.
Photo credit, DANIEL BELOUMOU OLOMO
A nurse prepares a Covid vaccine
6. Do I need a fourth dose of vaccine?
It should be noted that there is a difference between an “extra dose” and a “booster dose” of vaccine.
An additional dose, which may be a third or fourth dose, is offered by several countries for people with severely weakened immune systems, for example blood cancer patients or transplant patients.
The UK and US began offering third and fourth doses to these people last year when it became apparent that following the first two doses the vaccine did not provide sufficient protection once morest the virus. Covid infection.
The booster dose, on the other hand, is offered to the general population, to people who have already received two doses of the vaccine.
In early 2022, Israel and Chile began administering a fourth dose of the vaccine – or second booster dose – to large groups of the general population.
But other countries have felt that, for now, the data are not sufficient to justify the need for a fourth dose for the general population.
“At the moment, there is no evidence that a fourth dose is necessary or effective,” says immunologist Igancio Molina.
“Maybe a new booster dose will be needed in some groups, if time has passed and previous immunity has waned over the months. But, I stress, at the moment there is no no benefit to administering it,” he adds.
7. Will I need another dose of vaccine if another variant arises?
For now, we can only speculate. But as the immunology expert points out, SARS-Cov-2 having shown an incredible ability to change and mutate, everything will depend on the resistance of new variants to existing vaccines.
“If there is another variant that remains susceptible to current vaccines, then we won’t have a problem,” he says.
“But the fear of all immunologists is that at some point a variant resistant to the vaccines that we currently have will appear. And that would obviously lead to a situation of lack of protection.
“In other words, whether or not vaccines need to be tailored to the predominant variant at that time is something that we will have to analyze bit by bit.
