A woman over 80 years old receives the covid vaccine this Thursday in the Illumbe bullring, in San Sebastián. Javier Etxezarreta / EFE
This pandemic would have been much more terrible without the greatest ally that humanity has to defeat the coronavirus: the immune system. Thanks to him, the mortality of the pandemic is much lower than it could be, even in older people. Vaccines, our other great weapon, are nothing but an instrument to awaken the immune system and teach it to detect and destroy the coronavirus wherever it hides.
A new study has just brought good news about the immune efficacy of both people who already they have had an infection like those that have received the messenger RNA vaccine – Pfizer and Moderna. The work, led by researchers from the La Jolla vaccine center, in the United States, shows that the immune system of these people generates different types of white blood cells that are capable of neutralizing the most worrying variants of the coronavirus: British, South African, Brazilian and the new version detected in California.
These new forms of the virus carry several mutations that make it more contagious and possibly more virulent. The British variant —B.1.1.7— is already present in 100 countries. In Spain its prevalence ranges from 64% of cases to only 4% depending on the autonomous community. A preliminary study published last week indicates that in the United Kingdom variant B.1.1.7 is up to 90% more contagious and has caused 58% more deaths. It is not clear whether these additional deaths are due to additional virulence of the coronavirus or rather to a higher incidence that has pushed British hospitals further to the limit.
Recent laboratory studies using blood from patients have shown that some of these variants are capable to escape the action of antibodies, the proteins produced by the immune system responsible for preventing infection. Other studies suggest that the vaccines lose some effectiveness against the new variants. For example, Novavax, not yet approved in Europe, was 89% effective in a UK trial, but just 60% in South Africa . Janssen injection was 72% effective in the US, but only 57% in South Africa . This country has suspended the administration of the Oxford and AstraZeneca vaccine after observing an efficacy of just 22% in a preliminary trial. Still, vaccines do seem to be just as effective against newer versions of the virus in preventing severe covid and death.
The aforementioned studies have focused on studying antibodies, which are just one of many molecules and cells that the immune system relies on to stop infection or cleanse the body of viruses. La Jolla's work focuses on two immune system assets that are crucial for the body to orchestrate a complete defense. These are two types of white blood cells called CD4 + and CD8 +. The former does not serve so much to fight the virus directly as to command other units of the immune system to produce antibodies. They also recruit cytotoxic lymphocytes capable of identifying and killing already infected cells. The second type of white blood cell analyzed produces antiviral molecules that disable the pathogen and can also kill infected cells. The presence of these cells in the body implies that the person has developed a complete immune response against the new coronavirus SARS-CoV-2.
“Lymphocytes recognize both old and new variants. This means that although they do not prevent you from being infected with SARS-CoV-2, it is plausible that they will save you from suffering serious covid "
The study , still preliminary, has analyzed the levels of these two types of white blood cells in the blood of 11 people who were infected with coronavirus between July and October 2020 – before the new variants circulated – and that of 19 people who received RNA vaccines. The results show that these white blood cells can neutralize the "classic" virus and the four new variants with great effectiveness.
"These data are very good news," summarizes Alba Grifoni, co-author of the study. “Lymphocytes recognize both old and new variants. This means that although they do not prevent you from being infected with SARS-CoV-2, it is plausible that they will save you from suffering severe covid, "he highlights.
This same team had already shown that the immunity acquired after an infection lasts at least eight months and probably years . They also brought to light cases of patients who, despite having a genetic defect that prevented them from producing antibodies, had very mild infections due to the fact that their cellular immunity worked perfectly.
The results of this work are compatible with the future that is predicted. for this coronavirus: that as more people are immunized either by infection or by vaccination, the coronavirus will gradually turn into a mild cold , as it happens with other viruses of this family. This can force to update the vaccines from time to time, as it already happens with the flu. The authors of the work suggest that it may be necessary to create new versions of the vaccine that include more antigens – fragments of the virus to train the immune system – and not just protein S, which is what the virus uses to enter cells , which is one of those that accumulates the most potentially dangerous mutations.
“We must bear in mind that this study is still preliminary and with a small number of patients, but it is also very detailed and is supported by a very reliable group of scientists ”, Says Marcos López, president of the Spanish Society of Immunology. “The data provide optimism and help us understand why there has not been a wave of reinfections with the new variants. Most vaccinated people are not getting reinfected. These levels of lymphocytes guarantee that there is no serious disease, "he adds.
" These data are very positive because they assume that vaccinated people or those who were already infected with the coronavirus before the new variants appeared are protected from a second infection ”, Highlights Eva Cáceres , head of immunology at the Germans Trías i Pujol Hospital. This good news has a somewhat less positive side, because if the variants escape the antibodies this can lead to greater transmissibility and infectivity, although the virus does not cause disease in those already immunized, he adds. The question that remains to be answered is how long a person who has passed the infection or has been vaccinated is immune to the virus.
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