Despite high rates of vaccinated that are recorded in some countries, the numbers of the pandemic they do not seem to diminish. In recent weeks, there was even evidence of an increase in infections of Covid-19 comparable with those counted in the middle of the second or third wave. What is the reason and how could this trend be reversed?
With the reinstatement of curfews and restrictions on Italy (due to the increase in infections, admissions to intensive therapies and infections among those vaccinated), France (with greater controls on the arrival of travelers and nations on “red” lists) and United States (due to the rise in cases, hospitalizations and deaths), to name just a few countries, it would seem that the coronavirus only took a step back to gain momentum from the hand of the Delta variant.
“The protection that generate the vaccines is not so comprehensive as to prevent some patients they become infected, although it is robust enough to avoid, in its vast majority, serious forms ”, he pointed out to TN.com.ar the former president of the Argentine Society of Infectology and infectologist at the Muñiz Hospital, Lautaro de Vedia (MN 70640).
For its part, Luis Cámera, clinical physician (MN 51995) and member of the advisory committee of Alberto Fernandez, added: “Vaccines are not fully immunizing, there is a small percentage of people who become infected”.
At first, it was estimated that vaccines would be the solution to the pandemic. However, the evolution of the virus and emergence of new variants left at immunizations under the magnifying glass. The specialists clarify that vaccines are not completely infallible and emphasize that there will always be a number of people who may be infected even if they have complete schedules as a result of the permanent evolution of the virus.
“Undoubtedly, the immunity conferred by vaccines is not absolute, it does prevent serious forms. Both in phase 3 studies of the different vaccines and in real life (the follow-up that infectologists do), it is very rare for a vaccinated patient to evolve towards serious conditions, not impossible but it is very very rare. Immunity is not as complete, although it is generally robust enough to avoid serious forms, it does not avoid the light forms ”, emphasized De Vedia.
Cámera, meanwhile, appealed to an example to graph the difference: “It is not related to real numbers but it clarifies it, if there is any a thousand people vaccinated and a thousand not vaccinated, it is possible that, over a certain time, of the one thousand vaccinated 20 are infected and 100 of those not vaccinated are infected. The difference between 100 and 20 is 80, so the effectiveness of the vaccine is 80%. The effectiveness is not 100%”.
Antibodies and vaccination schedules
Another point that influences these infections is the presence of antibodies and how complete the vaccination schedule is. Even more before new variants that, in order to survive, they manage to evade the immune response and they develop characteristics that make them more infective.
“It may happen that some people, anecdotally, do not generate antibodies, but the vast majority do so to varying degrees. But also, vaccines have an effect on another part of immunity, which is the activation of B and T lymphocytes that generate what is called a cellular response, which recognize the virus as soon as they enter. Many people decrease the level of antibodies over time, however they are still immune due to the T lymphocyte response”, Highlighted Cámera.
Along these lines, De Vedia added: “In infectology we explain it as a fight between the aggressor and the victim: if the viral load that attacks me is very high and I have a not so high level of antibodies, the most likely infected me. But if I have a low viral load and a good level of antibodies, surely it will not happen to me ”.
That is why he stressed that, among the factors that can influence in this situation, they find “the age, the clinical conditions, the type of vaccines, if the scheme is complete and the weather what do I bring vaccinated. For example, if I get infected a week after being vaccinated, I still haven’t achieved a good antibody level, I need at least two weeks ”.
Furthermore, for both specialists, completing the vaccination schedule may be a relevant factor in the presence of SARS-CoV-2. “With a dose of any vaccine I will have a good level of antibodies, but with two doses I will have a better level. So the more complete the scheme is, the better protected I will be, but there are still people who, with two doses, can become infected”Warned de Vedia.
“The more complete the schemes, the more effective they are. With one dose, in our vaccines, it is achieved around 70% and with two it reaches 95%, approximately. With that of Sinopharm maybe a little less with the first dose, therefore we must try to complete the two doses as quickly as possible ”, completed Cámera.
Variants and a new target for herd immunity
If the constant presence of Covid-19 in the world could be summed up in a single soccer phrase, it could well be said that variants “ran the bow” to herd immunity. With which, the estimates of the specialists suffered the same changes as the pandemic itself.
“Herd immunity, previously calculated at 50 or 60%, could change with the appearance of the Delta variant which, for me, makes the herd immunity is not less than 80 or 85%. It is a very contagious virus and it was clearly seen in the United Kingdom and several countries in the northern hemisphere, where people who had not previously been infected and those who already had a dose are becoming infected, which it is necessary to have the two doses at the highest possible speed“Reflected the presidential adviser.
While de Vedia stressed: “Undoubtedly, the more people are vaccinated, the less the virus will circulate. Then, both the vaccinated and the entire population in general will have less probability of being infected. The closer we get to herd immunity, the better protected we will all be”.
Meanwhile, Cámera warned about a factor that could favorably collaborate with the arrival of the Delta variant: “This mutation has compromised places where conventional variants were no longer circulating, therefore entered a territory practically free of other viruses for its competition. This situation probably would not happen in Latin America, because we are always going to keep in mind, to some small degree, the Manaus (Gamma), the Andean (Lambda) and the British (Alpha) viruses, with which the entry of the Delta would be somewhat more difficult due to competition”.