How far away from collective immunity, which countries are on the verge of reaching it and what is the situation in Argentina

The end of jugulars, of social distance, of the pandemic. Almost from day one that we all wait for the coronavirus to end. Lots of risky dates. In 2020, we were talking about 2021, and now? The collective immunity, this possibility of having a high number of vaccinated population which allows slow the spread of the virus, was the goal to achieve from the start. But that goal fled.

Specialists assumed it would come with 60% of people vaccinated with two doses. The appearance of new variants, including Delta, has somewhat changed the panorama. This forces us to ask ourselves what collective immunity would entail today, which countries are approaching it and how far Argentina is lacking.

“At the beginning, we associated herd immunity with 60% of the vaccinated population. This was the case with the original variant, from Wuhan. Now with the new mutations we are faced with a higher viral load and infectivity», Affirms to Bugle Arnaldo Casiró, Head of the Infectious Diseases Department at Álvarez Hospital.

He says the strategy of giving a single dose and postponing the second, in the context of the vaccine shortage Argentina was facing, served to decrease mortality but not to gain group immunity since many continue to be infected.

For Casiró, the key today would be to have vaccinated with two doses to 80% of the population. “I’m saying that for the moment, with the variations that we know. The situation is very dynamic and can be modified “, he warns and specifies that later it will be necessary to see how long does this immunity last achieved and whether reinforcement will be required to support this scenario.

“The third dose, which some developers like Pfizer and Moderna are already working on, it may need to be given as booster To increase the level of antibodies that i can go fall or face more mutation», He emphasizes.

The arrival of millions of doses in recent months has renewed enthusiasm for the possibilities of obtaining this famous immunity. However, the percentage of vaccinated in Argentina with two doses continues to be very low, compared to what is happening in other countries and thinking of the 80% target.

According to the Public Vaccination Monitor, Argentina distributed this Sunday 35,510,374 doses of which already applied approximately 29,723,228. The vast majority worked as first doses. Out of the total, just 6,008,542 people completed their program. Which equates to a little more than 16%.

Israel, one of the countries taken as an example of immunization, has more than 58% of its population with two doses. Meanwhile, the UK has managed to 55% complete your diagram, based on data collected by the Johns Hopkins University of Medicine website.

Spain is betting on 53%; Canada, for 54%; The United States reached 49%; Italy, at 47%.

Above is Malta with 72%, Iceland with 70% and the United Arab Emirates with 69%.

The African continent is the one with the worst vaccination rates, with a few exceptions such as Morocco which has 26% with two doses. South Africa is close to 3% while in Mozambique only 0.99% have completed the program.

From our region, Chile has 62% of its population with two doses and Uruguay, 61%. Brazil and Mexico overtake Argentina, but not by a significant difference, with 17% of those immune. At the other extreme, there is Venezuela with 3.8; and Paraguay with 2%, among others.

Obstacles in the race for collective immunity

Among the obstacles to achieving the desired immunity levels, Casiró highlights the delay upon arrival of component 2 of Sputnik V, which has led many people to already exceed the maximum recommended deadline for its application, which was 90 days.

Another obstacle, according to the specialist, has to do with vaccination of minors. “Even with the recommendation of the European Medicines Agency for the emergency use of Moderna in adolescents, we should still receive a lot more vaccines to cover this segment”, believes Casiró, who prefers not to put a date, even if he anticipates it is probable that collective immunity will be 2022.

“Also, the life before will not return. Not even with group immunity, ”he asks for clarification. “It is likely that with 80% of the vaccinated population deaths drop a lot and it can circulate in open spaces without a chin strap and increase the capacity in closed places. Also open the borders. Corn anything massive in places without good ventilation will not come back», He emphasizes.

And he adds, “It’s likely that we’ll have small outbreaks, as happened to Israel with the Delta variant, and that we’ll have to partially go back on some of the openings. Here we will also have a lot trial and error”.

Eduardo López, infectologist at Gutiérrez Hospital and member of the expert committee advising the president, agrees that the concept of herd immunity was changing as new variants were introduced.

“There is no group immunity with a single dose. The complete diagram is required and the percentage increases with the arrival of mutations. Initially, we were talking about reaching between 60 and 70%. Today we should locate ourselves between 70% and 80%”Says López, given the presence of the Gamma variant (Manaus) and the risks due to the arrival of Delta (India) and Beta (South Africa).

Explain that herd immunity varies with each disease and is achieved when a certain number of people are vaccinated, allowing the unvaccinated have no one to catch it. “This is when the virus is blocked because it stops circulating,” he explains.

The time it will take to get there, López says, will depend on the dose availability and vaccination rate. “Out of 10 vaccines applied today, 8 are first doses and 2 are seconds. Ideally, we could achieve the expected immunization figures by three or four months“, He shares.

And it shows that beyond the percentage of vaccinated with two doses, it would be necessary to see how many recovered have already received a dose, since “The immunity generated by the disease also matters”.

“We should emulate England, Israel, the United Arab Emirates and Iceland,” he remarks. And he assures us that there are other territories which are experiencing a much more complicated situation than ours, such as a large part of Africa and certain Latin American countries.

Not easy how long can immunity last. “Among the recovered, we know that at least 9 months and among the vaccinated, it will surely be longer. This aspect will also have an influence. The other relevant point is that no significant mutation appears to generate a new strain which requires another vaccine, ”adds López.

Jorge Quarleri, biochemist and principal researcher at Conicet, has a more skeptical look in relation to the chances of obtaining collective immunity. “First we have to think that about 30% of Argentina’s population – some 13,000,000 people – are under the age of 18 and we still don’t know when they will be able to get vaccinated. Of the remaining 70%, only 12% have already received both doses, ”he says.

As obstacles, he points to the delay in the arrival of the second dose of Sputnik V, which, according to him, will be resolved when the possibility of combining it with another vaccine is confirmed. In the meantime, he is referring to a new study related to AstraZeneca, which showed that by spacing out its doses by more than 70 days, the effectiveness of this vaccine drops 5 times, according to the review published in June. The Lancet.

“The failures we may have in relation to efficiency because of what we have done with the intervals it may also have an impact on collective immunity. For now, we have this data from AstraZeneca. Sputnik V and Sinopharm did not directly present information in this regard, ”explains Quarleri.

Another element to consider is related to the duration of natural and artificial immunity. “In Israel, for example, the vaccination was uniform and the time limits between doses were respected. There are people here who were vaccinated in January and others who will be finishing their program in December. Some people waited months between one dose and the next. You have to see what happens with all of this, ”underlines Quarleri.

“I don’t know if, with 80% of the vaccinated population, collective immunity will be achieved, if we consider it as a kind of bullet proof vest against infections. I think that, in this case, the decrease in mortality will be very noticeable, but the measures of prophylaxis because surely there will be people who will continue to be contagious“, he says.

And he warns: “In a globalized world collective immunity is not a national phenomenon. The WHO has already said, we must reach the poorest countries because if new variants are not going to appear they will laugh at those who have up to 6 doses of vaccine ”.

MG