A race against time.
This is how the mobilization to vaccinate the world population against the coronavirus and restore normality as quickly as possible could be described.
Until last January 23, they were already more than 60 million people who have received some dose of the vaccines against the pathogen.
But as more countries accelerate or begin their campaigns, several unknowns continue to worry scientists, governments and ordinary citizens.
It is still unknown how long the immunity offered by vaccines lasts or if the new variants of the virus that emerge around the world will become resistant and render them unusable.
BBC Mundo explains four key unknowns almost two months after starting the most massive immunization in our history.
1. How long do vaccines provide immunity?
How immune we become after passing the coronavirus or getting vaccinated is one of the questions that we have asked ourselves the most in recent months.
One year after the start of the pandemic, the first studies on medium-long-term immunity have already come to light.
According to the La Jolla Institute of Immunology, in California, several of the immune responses after overcoming the coronavirus infection remained active during at least six months.
It is similar to the time that Public Health of England handles, which indicates that most patients who had covid are protected for at least five months.
Considering that it has not been much longer since the first infections, several scientists are confident that immunity will last longer, even years.
Of course, this is not a universal rule. Each patient can develop more or less protection and the possibility of reinfection or not will depend on that.
Something similar happens with vaccines.
“It is difficult to say how long immunity can last because barely hemos started to vaccinate and may vary depending on the patient and the type of vaccine, but perhaps between 6 and 12 months ”, says to BBC Mundo Dr. Julian Tang, virologist at the University of Leicester, in the United Kingdom.
Dr. Andrew Badley, professor of molecular medicine at the Mayo Clinic in the United States, is more optimistic: “I am confident that the effects of vaccination and immunity can persist several years”.
“It will also be important to analyze in detail the cases of infected with the new variants, which were not widespread in the first analyzes, and to observe how patients respond after the vaccine,” adds Badley.
2. Is it possible to get coronavirus after getting vaccinated?
Yes, it is possible, and for several reasons.
The first is that the protection offered by most vaccinesdoes not activate until two to three weeks after receiving the first or only dose, depending on the type of vaccine.
“If you are exposed to the virus a day or a week after injecting yourself, you are still vulnerable to the infection and you can transmit the virus to other people,” Tang explained to BBC Mundo.
But even if one is exposed to the virus several weeks after receiving the required doses, it is possible to become infected again.
“The available data suggest that some individuals can continue to be infected with covid, although they would have less virus and consequently less ill than those who have not been infected or vaccinated. In the same way, I think the virus, once vaccinated, will be more difficult to transmitBadley adds.
Therefore, there is some consensus that vaccines seem to protect very effectively a considerable number of individuals, but the extent to which they prevent infection and transmission of the infection remains unknown.
“This is a very heterogeneous virus and it produces very different symptoms depending on the patient. The same will happen with vaccines. Some will have a very powerful immune reaction that will soon prevent the virus from reproducing in them. While in others the answer will not be as complete and will allow a bit of reproduction and transmission, ”José Manuel Bautista, professor at the Department of Biochemistry and Molecular Biology at the Complutense University of Madrid, in Spain, tells BBC Mundo.
3. Will vaccines protect against new mutations and variants of the coronavirus?
This is perhaps the biggest concern around right now. Viruses constantly mutate, and sometimes they do so so much that they become more resistant to vaccines, so they need to be modified.
It is the fear that exists with the coronavirus variants identified in South Africa or the United Kingdom, for example, of which Cases have been registered in other countries and they have even become dominant due to their greater infectivity.
However, it is still too early to say exactly whether these variants are resistant to the vaccine or not.
Moderna announced on Monday that its vaccine was still effective against the UK and South African variants, although in the case of the South African it would produce a new form of extra vaccine that can be used to boost protection.
Pfizer and BioNTech also claim that their compound neutralizes the new variants.
“In the same way, it must be taken into account that although the approved vaccines are very effective, they are not 100% against any variant of the virusNot even the original, ”says Badley of the Mayo Clinic.
“Vaccine protection will depend on how different the new variants are from the old ones,” explains Tang.
In summary, it is unknown whether the new variants that have emerged will be resistant to vaccines, but the need for governments and health departments to monitor and identify emerging variants to assess whether available therapies can neutralize them is clear.
4. How many doses and in what period should the vaccines be administered?
The Pfizer, Moderna and the University of Oxford and AstraZeneca vaccines, for example, are given in two doses.
In the case of Pfizer and Moderna, they recommend that these two doses be administered with a three-week gap between the first and second.
But in late 2020, the UK announced that it would prioritize vaccinating as many people as possible with the first dose and that it would offer the second for up to three months after the first.
The UK move sparked an international debate about the best way to vaccinate, but Pfizer and most of the global scientific community preferred to stick to the evidence from clinical trials: one dose today and the second at 21 days.
The WHO ruled on this and also recommended administering them every 21 or 28 days, although they admitted that this interval could be extended to a maximum of six weeks in exceptional cases.
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