A new study has shown that immunity to coronavirus is short-lived if a patient has mild or no symptoms. According to Chinese scientists, the cells responsible for the long-term ability to fight the virus were not found in such people. And the absence of these cells calls into question the ability of patients to elicit the full immune response needed to develop a vaccine.
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Patients with mild symptoms do not acquire long-term immunity against the coronavirus that causes COVID-19, according to a new study by Chinese military scientists. South China Morning Post.
A team of researchers led by Dr. Ye Lilin of the Institute of Immunology at the Army Medical University in Chongqing found that only patients recovering from severe or moderate conditions had memory immune cells targeting the Sars-CoV-2 virus.
It is estimated that about 80 percent of people who test positive for the coronavirus have mild or no symptoms. Whether such people could get infected again is now one of the biggest concerns for the research community amid fears that a larger and deadlier wave of coronavirus infection could occur in the northern hemisphere this fall.
The new discovery “will lay the foundation for the rational development of effective vaccines,” Dr. Yeh and colleagues said in an article published on the online portal medrxiv.org on Monday.
More than 400 vaccines have been developed and are in clinical trials worldwide, according to a recent study. Preliminary results indicate that most of these candidate vaccines can elicit varying degrees of antibody response.
However, the question remains as to whether the induced immune defense can last and for how long. A growing body of research shows that some infected patients lose antibodies quickly.
Military researchers examined blood samples taken from nearly 60 patients in Chongqing, southwestern China, at various stages of the disease. Their condition ranged from severe to asymptomatic. These patients were then compared with eight healthy volunteers who had no previous exposure to the virus.
According to the study participants, the difference was “striking.” According to their analysis, patients without symptoms or with mild symptoms were unable to generate any resistant cells targeting the coronavirus. Memory B cells are generated by the immune system and are capable of recognizing the virus and producing antibodies even decades after infection.
However, the researchers noticed an increase in the number of “helpers” and “killer” T cells in these patients. These T cells are another type of immune cell that viruses can attack, but they don’t specifically target Sars-CoV-2. Dr. Yeh suspects that these are remnants of previous infections caused by other types of coronavirus that led to the simple flu.
Patients who suffered from coronavirus, and some of them were close to death within several weeks, acquired a large number of memory B cells, so they were better prepared to fend off the new attack of COVID-19.
But the study found that these very sick patients were unable to produce enough T-lymphocytes, if any. The reason for this phenomenon is unclear.
In any case, according to Dr. Ye and colleagues, the patients’ immune response was incomplete. B cells and T cells usually need to work together to ward off a viral attack. Induction of both of these immune responses could be critical for a vaccine to prevent Sars-CoV-2 infection, they said.
Some countries that have failed to stop the spread of the outbreak have expressed hope that their populations will eventually acquire herd immunity.
White House COVID-19 adviser Dr. Scott Atlas argued that infection of low-risk groups such as young people would not result in more deaths.
Recall that recently, Hong Kong reported the world’s first confirmed case of re-infection, when a patient contracted the coronavirus twice with an interval of several months. It was followed by similar reports from other parts of the world, including the United States and India, which currently lead the largest number of infections that cause COVID-19.
In a study published recently in the authoritative edition of The Lancet, it is said that a 25-year-old man from Nevada showed mild symptoms during the first infection with the coronavirus, but after reinfection he developed a serious condition.
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