Argentina questioned the need for a second dose of Sputnik for those who had recovered

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Argentina questioned the need for a second dose of Sputnik for those who had recovered
Argentina questioned the need for a second dose of Sputnik for those who had recovered
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Argentine researchers studied the reaction of the body of those who had had Covid-19 to the first and second doses of Sputnik and discovered an unexpected fact: for some reason, after the second dose, the level of antibodies in those who had recovered did not increase and even dropped slightly. For this reason, they propose to vaccinate coronavirus survivors only with the first dose of the Russian vaccine. This will also make it possible to quickly vaccinate the local population: the demand for Sputnik in Argentina is extremely high, and supplies from Russia are still limited. The work can be of significant practical importance for dozens of other countries where Sputnik is used.

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Today, scientists do not have an accurate and reliable understanding of what level of antibodies reliably protects its carrier from coronavirus. This is due to the fact that the situation is constantly changing. Until recently, it was believed that cellular immunity would protect a person even after a decrease in the level of antibodies in the blood of a vaccinated (or recovered) person. However, in June 2021, it was discovered that in the case of "delta", cellular immunity is activated with a delay of three days, during which this strain of coronavirus has time to cause significant harm to the body. All this forces researchers to focus on the highest possible level of antibodies as an approximate guideline in terms of protecting the body from the virus.

The authors of the new work in Cell Reports Medicine tried to find out exactly what level of antibody protection in those who were not sick and were vaccinated with Sputnik, as well as in those who had been ill and then were vaccinated with the Russian vaccine. After the first dose, 94% of non-ill patients showed IgG antibodies to coronavirus. Their average antibody titer was 104, 2 international units per milliliter (IU / ml, IU / ml). After the second dose, antibodies were found in 100% of non-ill patients, and the average titer reached 787.8 IU / ml. An approximate level that gives protection above 50% is considered to be a level of at least 100 IU / ml, then protection is nonlinearly related to the level of antibodies. In other words, a tenfold increase in the level of antibodies does not increase the protective efficacy by the same tenfold.

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It should be added that 1000 IU / ml is considered the standard high protective level of antibodies. At first glance, it may seem that 787.8 IU / ml is not enough. However, it should be borne in mind that these figures were obtained on a cohort of 62 non-recovered study participants. Among them were the elderly, who normally show lower antibodies than people under the age of 60.

Very unusual results were achieved for the recovered participants in the study - a total of 227 people. On average, before vaccination, their titer was only 181.1 IU / ml, which is noticeably lower than the high protective or post-vaccine level recorded in the vaccinated. This is normal: as we already wrote, the immunity of those who have been ill is on average lower than that of the vaccinated, and this is so not only for the coronavirus, but also, for example, for the human papillomavirus.

Twenty-one days after the first dose of Sputnik, the patients who had been ill had 6356 IU / ml, that is, the level of antibodies with which the risk of getting sick is vanishingly small. Surprisingly, 21 days after the second vaccination, this level dropped to 5609 IU / ml. This does not mean that the second vaccination lowers immunity: the fact is that very high protective levels of antibodies generally rarely last long in a person, since immunity normally relies on cellular memory and over time reduces the level of antibodies.

What do such unusual data indicate?

But the Argentinean figures mean that there is no point in administering the second dose of Sputnik to symptomatic patients: it cannot significantly increase the titer of their antibodies. This noticeably differs the situation from that which was recorded for those who were revaccinated by Sputnik (or Pfizer) who did not recover.According to data from chats of "popular vaccination", those who did not have Covid-19, the level of antibodies increases both after the first revaccination vaccination, and after the second, and the increase after the second is very significant.

The researchers especially note that those who have recovered and after only the first dose receive such a high level of antibody protection that they stand out sharply against the background of simply vaccinated.

We would like to draw the attention of readers that you should not try to estimate your antibody level from this work, because most of the existing commercial antibody tests do not give their result in international units per milliliter. To translate test results into international units, you need to know the levels of conformity of "in-test" units to international ones. For example, if AU / ml is written in the Abbot test, then the digital total of the test must be divided by seven - then you will get the number in international units per milliliter. If you have a Roche test, then (in Russia, abroad there are other tests of the same manufacturer), on the one hand, you do not need to translate anything. On the other hand, the sensitivity of the test from above is limited to 250 units (there are also elements of "nonlinearity" in the test), which makes it not quite informative. The Abbot test is generally more informative.

Most importantly, antibodies normally reach a maximum three to four weeks after the second vaccination, and then begin to decline. The trajectory of the decline depends on how many antibodies you had at the very beginning. The more there were, the more slowly their number decreases. The less - the faster their level will fall in the future.

Therefore, the majority will not see the exceptionally high figures given in the work, if they did not measure antibodies on the 21st day after the second injection. Or immediately after an illness, if we are talking about those who have just been ill. But a lower (than in the study above) level of antibodies does not necessarily mean that your defense is low: the schedule of antibody decline is slightly different for everyone.

In most cases, the level of antibodies after vaccination with Sputnik reliably protects against covid for about six months. However, in Israel's experience with the Pfizer vaccine, protection may be lower at the end of this 6-month period than at the beginning. We have already written about why and why revaccination is needed, how it affects antibodies.

The work of Argentine researchers has some limitations. All the subjects studied were medical workers of the local health care system. As practice shows, doctors and nurses are faced with a large amount of viral load, therefore they often get sick in a symptomatic acute form, which leads to significant, in comparison with asymptomatic, antibody titers. This means that their immunity after the first vaccination with "Sputnik" may be stronger than usual.

Why is Argentina being vaccinated mainly with Sputnik and not with whole virion vaccines like CoviVac?

Today Argentina vaccinates the population mainly with Sputnik. Some of the vaccinations are made with the vaccine developed by AstraZeneca and the PRC, but their popularity is somewhat less. This happens even though the number of mild side effects after Sputnik is noticeably higher than after AstraZeneca and the Chinese whole virion vaccine. The reasons for this popularity are the higher efficiency of Sputnik in comparison with competitors and the fact that it produces severe adverse events 9% less frequently than the drug developed by AstraZeneca.

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The reasons for Argentine's choice of Sputnik are easy to understand when comparing the Argentine coronavirus situation with neighboring Chile. In Chile, more than 68% are vaccinated, but the covid mortality rate during the vaccination period does not show a clear downward trend - while in Argentina, on the contrary, it has significantly decreased from the peak values. The reason is that both Chile and Brazil use mainly the whole-virion Chinese vaccine - the same type as the Russian KoviVac. With regard to coronavirus, whole-virion vaccines, as we have already written, are less effective than vector vaccines.

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Argentina is more than twice ahead of Russia in terms of the share of vaccinated population: its population is not covered by anti-vaccination sentiments, therefore 43, 16% of the population are vaccinated there, against less than 20% in our country.

At the same time, access to Sputnik there is much weaker than the need for it. Argentina makes a vaccine from a substance imported from Russia, while it is only enough for two million doses per month. The population of the republic is 35 million, only a third is vaccinated. This creates an interest among local researchers in the question of whether it is possible to speed up the process, including through single-dose vaccinations for those who have been ill.

The conclusions of the Argentines, however, are of great importance for dozens of other countries using our vaccine, including Russia. The fact is that the Argentinean authorities and scientists publish research on Sputnik relatively quickly, while in Russia the statistics of the Ministry of Health on this issue are either not published at all, or are only briefly indicated in the speeches of officials.

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