Is Covid’s reinfection more serious for some of us?

Analysis: For some people, reinfection may exacerbate symptoms compared to the initial infection

To Ben Krishna, WhenCambridge diversity

Covid’s pandemic has been going on for over two years. During this time SARS-CoV-2 (The virus that causes Covid-19) mutates slowly and Avoid the immune system Enough to infect humans many times.

Many of us are already infected with Covid, so it’s not surprising that many people catch the virus even the second or third time.This has been Especially noticeable Since the advent of the Omicron variant since December 2021.

But can re-infection make you feel better or worse than when you were first infected with Covid? Not only is this a question that many are interested in, but it is also an important issue from a public health perspective.

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From this week’s RTÉ Radio 1. Dr. Cilliande Gascun of the National Institute of Virology for Virus References on the Summer Rise of Covid Cases

If the symptoms get worse each time someone gets infected, the pandemic is expected to get worse as people get more and more ill. A Zero Corona Strategy It’s the only way to avoid a wave of serious illness.

The alternatives are almost the exact opposite. If each subsequent infection is less severe, the pandemic will eventually disappear spontaneously without the need for masking, quarantine, blockade, or other means.

So what do you say the evidence is?

Recently Preprint (An article published online prior to peer review) was interpreted to suggest that the symptoms of Covid’s reinfection were worse than those of the initial infection. However, the author did not specifically investigate the severity of the symptoms. Within 6 months of infection, they investigated possible causes of death, hospitalization, and various health problems. Researchers have concluded that these measures have worsened after reinfection.

This is not good news, but the results need to be interpreted carefully. The data used in this study came from electronic medical records of more than 5 million U.S. Army veterans, of whom more than 290,000 had Covid at least once.

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From Today With Claire Byrne on RTÉ Radio 1, Professor Cliona O’Farrelly of TCD talks about people who are still “Covid-Free” after two and a half years.

First, the groups surveyed were already at increased risk of experiencing worse results compared to the overall population. The average age is 60 years, about 20% smoke, and more than 80% of people infected with Covid have not been vaccinated, so the results may not apply to the general public.

Second, the re-infected group analysis Immediately after reinfection, the first infected group was not analyzed until 30 days after infection. This means that the results observed with reinfection include all early Covid symptoms (headache, cough, malaise, etc.) that other groups may have recovered. The data include symptoms or health problems that occurred during the study period, including one group of acute infections, which distorts the results and appears to exacerbate reinfection.

So what does this preprint show? Although reinfection suggests an increased general risk of health problems, it is worth remembering that the study population is already at high risk.Respiratory tract infections such as influenza range Major cause With worldwide deaths, it is not entirely surprising that extra respiratory infections increase the risk of human health problems. However, this finding is not the same as the more severe symptoms of reinfection.

How immunological memory works

This study caused some turmoil on Twitter. This is because each subsequent infection tends to cause milder symptoms than the first, or at least is expected to change little.

Immunological memory It is a phenomenon in which the immune system “remembers” past infections, reacts more quickly and effectively to reinfections, and reduces the spread of the virus and common symptoms. This is because the immune system makes antibodies and is a type of white blood cell called a T cell at the time of initial infection. The immune system then reuses the same antibodies and T cells to fight reinfection.

Many latest vaccines ( COVID vaccine) Is based on this concept – “training” the immune system to remember the virus next time.For many illnesses like smallpox, measles Once the chickenpox survives the disease, it boosts immunity and significantly reduces the severity of reinfection. One exception is dengue fever, where the immune system can actually make antibodies that help reinfection. Exacerbate symptoms In some cases.

It’s not the same for everyone

With Covid, studies of reinfection tend to focus on death and hospitalization because it is easier to measure than symptoms.Generally, they are re-infected Not so serious From the first infection.

You may think that “my second infection hit me harder than the first.” It is believed that some people may experience worse symptoms due to reinfection compared to the initial infection. This can be due to several factors. Different strains can cause more serious symptoms such as delta. Probably tougher From beta. A Higher initial dose A viral infection (for example, if some people have Covid sneezing) can spread more virus before the immune system controls the infection.

I’m worried if people who had mild symptoms at the time of the first infection but became very ill due to reinfection began to be hospitalized.

Finally, as the immune response declines over time, symptoms can worsen. For example, if the first infection occurred shortly after vaccination, but re-infected a few months later when antibody levels dropped, it makes sense that the first infection was mild.

These things happen to individual people, but they are unlikely to play a major role in large populations as a whole. I am worried if there is a tendency for hospitalization among people who had mild symptoms at the time of the initial infection but became very ill due to reinfection. So far, I haven’t seen any evidence of this.

Ben Krishna I am a postdoctoral researcher in immunology and virology. University of Cambridge..This article was originally published by conversation..

The views expressed here are those of the author and do not represent or reflect the views of RTÉ.