contagion even with two doses and when do they expect community circulation

Delta is still on everyone’s lips and, according to specialists and government health referents, there is little left to confirm the community circulation in the country of this variant of the coronavirus. For a long time, we kept saying that we had to complete immunization schedules to mitigate its impact, which has already caused the first death in the country on Sunday.

However, it is not yet clear how it behaves in those who have received both doses. Could these people, who now represent 25% of the population, become infected and spread? The answer is yes. It is from there that two experts explain what are the chances of contracting Delta in “immune” people, if they are expected to have severe symptoms and what to do to stop its progression.

“We know that Delta partially escapes the action of vaccines and that for this reason both doses are necessary. Completing the diagrams is very helpful in preventing serious illnesses, but not if the contagion“, He says Bugle Jorge Geffner, doctor in biochemistry, senior researcher at Conicet and professor of immunology at UBA School of Medicine.

Mouth, nose and throat

The trigger for fixing this problem is a report from the United States Centers for Disease Control and Prevention (CDC). “The agency said that in some areas, people vaccinated they could avoid the jugular and now they had to back offSays Geffner. This is after confirming that during the first days of the Delta infection the virus remains and can be amplified in the upper respiratory tract of the vaccinated person. It’s inside mouth, nose or throat.

” During about 5 days, vaccinated infected people can transmit the virus at levels similar to those of an unvaccinated person. But then, due to the effect of antibodies, the virus does not progress to the lower airways or lungs and this is how, in most cases, complications such as bilateral pneumonia are avoided, ”he says.

He specifies that the situation reported is with two doses of Pfizer although he considers that the panorama is similar with complete schedules of other vaccines, “either Sputnik V, AstraZeneca, Sinopharm or combined”.

As an example of the importance of two doses against serious illness, Geffner provides collected data on what happens one day in the Houston Medical Center and in the Perry Hospital the United States. “On August 9, there were 81 hospitalized between the two health centers: 72 unvaccinated and 9 vaccinated. 23 came to intensive care, none of them with the vaccine, and of these 23, 11 were broken down, ”he explains.

In the same vein, the specialist shares the reasons why he insists so much on completing the diagrams. “Vaccines generate antibodies, which are used to block a small part of the protein S – RBD – which the virus uses to bind to and infect cells in the body. The available vaccines are made with the old RBD, that of Wuhan original virus. The mutations that resulted in the Delta variant altered RBD. This makes it harder for the antibodies to recognize it and that both doses are needed. The same happens with South African variant“, To explain.

And it adds details on the effectiveness in terms of protecting against infection by comparing Delta with Alpha (UK variant) and what happens with one or two doses of Pfizer and AstraZeneca (separately), according to a study published in July. of this year in the New England Journal of Medicine.

The percentage of effectiveness is nearly 33% in those who received a dose and against Delta, against 50% against Alpha. The percentages are between 60% and 88% with two doses, the level of protection with Pfizer being higher. “And, by extrapolating the data, the levels against serious infections would exceed the 90% with two doses, ”remarks Geffner.

Based on this information, he concludes that two-dose vaccination is essential. “Fortunately, there is a good uptake in the country and it doesn’t happen like in the United States, where between 30% and 35% of adults have chosen not to be vaccinated. We must continue to supplement schedules with either homologous or heterologous vaccination. Progress is being made but more slowly than we need, ”he assures us.

According to the researcher de Conicet, now that we know that even with two doses the person is contagious, it is very important that the social distance, that the meetings take place at outdoors or in ventilated areas and that the chin strap is used.

“The drop in the number of cases and severe cases is leading to new openings, which is good. But there are decisions like the one that boys do not use chin straps in schools that do not seem appropriate to me, ”expresses.

Meanwhile, he maintains that within a month we will surely have Delta community traffic. “I do not know the magnitude, we do not yet know if we will experience something similar to what is happening in Europe or it could happen like in Brazil, where the Manaus variant continues to predominate,” he said.

And he adds: “The road with Delta installed must also be accompanied by more tests and for a good epidemiological surveillance of the genomic sequencing”.

Jorge Quarleri, a biochemist, professor of microbiology at the UBA School of Medicine and a senior researcher at Conicet, agrees with Geffner that the virus infects the upper respiratory tract of people with a full vaccination schedule.

“At the moment viral load levels are similar between vaccinated and unvaccinated. The difference appears later, when the infection wants to develop to the lower pathways. This is where he finds the resistance of the response generated by the vaccine and, therefore, it is expected that those with two doses will not become seriously ill, ”he explains.

“On the contrary, the unvaccinated have a higher risk of contracting serious illness, with a higher rate of hospitalization and bad prognosis», He emphasizes.

He also agrees that for an average of 5 days the virus can survive and reproduce in the nose, mouth or throat and the person is at risk of infecting it. “In some cases it can spread more and in others the viral load will drop sooner. Age is one of the factors that influence, also the time that has passed since the infected person was vaccinated, ”he notes.

And that refers to the results of an unpublished manuscript of a study conducted between May and June on a delta epidemic in China’s Guangdong province. “From this work, it appears that people infected with Delta are more likely to spreading the virus before symptoms develop than those infected with other variants, ”he emphasizes.

“A thousand times bigger”

He says airborne transmission is much higher than with other mutations (between 40% and 60% more contagious) and that, for all of this, the jugular is essential. “The viral load is a thousand times higher with Delta if it is compared to others, ”he warns, based on a pre-publication produced by authors from China and England.

“Now is not the time to slack off in preventing contagion. Those who have done so now are back with many cases. I mean the United States, Great Britain and Israel, ”he emphasizes.

And he affirms that having 25% of Argentines with two doses is still not enough: “We must drastically increase the figures before Delta circulates in a community manner. It should also be taken into account that two weeks after the application of the second dose is necessary to obtain a strong immune response. With a single dose, protection is close to 30%”.

Asked about those who are vaccinated and have had the Covid, Quarleri maintains that the risk of contagion is lower. “The person who has had the disease in the past probably has higher levels of protection in the upper airways because the virus entered there. This robust mucosal immunity it is generally not achieved with traditional vaccines. For this, aerosol vaccines administered by the nasal route are being developed, ”he concludes.

MG – EMJ