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The importance of the two doses of the vaccine to deal with the Indian variant

In the UK, the Indian variant has spread very quickly, also among people vaccinated with a single dose

They have found that the Pfizer and AstraZeneca vaccines, with a single dose, greatly reduce their effectiveness against the Indian variant

There are hardly any admitted among those vaccinated with two doses: “The level of antibodies rises exponentially with the second”

To know how the Indian variant works, UK is still the best lab. Because in that country it is spreading like wildfire, just as the British Health Minister himself predicted a couple of weeks ago. The B1617.2 It is already behind half of the country’s new covid cases, and potentially involved “by up to three-quarters,” according to Matt Hancock. It is already the dominant variant.

It is much more contagious than any of the previous ones and it also has a certain ability to evade antibodies. Its advantages over the other variants are clearly seen in this table prepared by the American scientist Eric Topol.

Eric Topol

This variant has made the curve of covid cases to skyrocket again, in one of the countries with the highest vaccination rates. The Indian variant is mainly spread among the unvaccinated population. But not only. Also -and this is the most worrying- among those vaccinated with a single dose.

33% effectiveness with a single dose

there is already scientific evidence on the level of protection provided by vaccines that are being inoculated there –AstraZeneca and Pfizer– compared to the variants that circulate the most (the B117 or British variant and the B1617.2 or Indian variant). And it has been seen that, In the case of India, the efficacy of the vaccines diminishes much more than with the British one.

A study by the British Public Health Service (PHE) has found 33% effectiveness of both vaccines after the first dose, in the case of the B1617.2 variant, something that would not be enough to face it. In contrast, after the two doses, the effectiveness of both vaccines is very high: 88% with Pfizer and 60% with AstraZeneca.

It is the first study on the effectiveness of vaccines against this variant. And its conclusion is clear. “Our findings on reduced efficacy of vaccines after the first dose supports the idea of ​​expanding two-dose vaccination among vulnerable groups, in the context of the circulation of B1617.2 ”, conclude the authors.

Exponential increase in antibodies with the second

Why is this happening? Why is there such a difference in the effectiveness of the vaccine with one or two doses? He explains it immunologist at the Hospital Clínico de Santiago José Gómez Rial.The first dose primes our immune system, but the important one is the second. The first prepares the immune system at the level of memory cell production, above all … but at the level of antibodies, the difference is brutal between the first and the second dose ”. This occurs in all vaccines, “that’s why almost all have two doses.”

But in covid vaccines, you also have to take into account the speed with which they were made. And its main objective, like emergency vaccinations: prevent deaths from covid and severe disease. “With one dose you are getting what you wanted, that is, protect against serious illness. Although vaccinated people are becoming infected, there are hardly any deaths, nor so many serious cases. But if we go to what is to protect against transmission, a single dose does not arrive “, warns Gómez Rial.

This is, now, the second objective of vaccines: stop the transmission of the virus and its variants. But “for this we need two doses.” And explain why. “Because of the power of the immune response: our immune system reacts exponentially with each dose. The antibody level rises exponentially with the second. Thus, there is much more probability of stopping the infection, and also the transmission ”.

UK speeds up second doses

In the United Kingdom there are 22 million people who have completed both doses of the vaccine. And almost twice as many, about 40 million, are vaccinated with a single dose. This is the result of a vaccination strategy that opted to immunize as soon as possible the largest number of people, postponing the booster dose in all of them.

The thing was going well, but the irruption of the Indian variant on the board has changed the rules of the game. So much so that the government decided change strategy and accelerate the inoculation of second doses in the most vulnerable population. And they are already doing it. Above all, in the areas of the country where it is causing the most problems: the Bolton, Blackburn or Bedford outbreaks.

Because the data that reality offers are eloquent. Hancock himself warned last week that Of the 49 people hospitalized in Bolton after being infected with the new variant, only 5 were vaccinated with the two doses.

More cases, but no more deaths

Covid cases are skyrocketing in that country, but there is not a sharp increase in hospitalizations and deaths are occurring “predominantly among older people who have not been vaccinated”. Vaccines, therefore, are doing their job. Hancock says they are “severing the link between covid cases, hospitalizations and deaths.” But at the same time, it urges the population to always accept the second dose.

On Spain still there are not many cases of the Indian variant, nor community transmission, but Gómez Rial insists on the same: “The desirable thing is to always have all the protection, no one is left with a single dose. It is necessary to be clear about the importance of completing the guideline as soon as possible. The worst option, and more in this scenario (in reference to the Indian variant), is to stay with a single dose ”.

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