Why do young people die from COVID-19 and 90-year-olds do?

Little is known about immunity to the SARS-COV-2 virus: why is infection a trivial infection for some and a deadly threat for others? Does having an infection provide permanent immunity – and for how long? Why do young people sometimes die from COVID-19, and sometimes centenarians do?

1. Although the coronavirus is the main topic that the whole world has been living on for six months, we still do not know the answers to many questions about it
2. In general, the virus is most dangerous to the elderly and the sick, but it happens that healthy XNUMX-year-olds and even children die of it. Why?
3. It is known that having a disease makes us immune to it for some time. According to reports, antibodies in the blood last two to three months. So how to explain people who get sick for the second time shortly after recovery?
4. Earlier estimates by epidemiologists indicated that group immunity to SARS-CoV-2 appears with immunization of 60 percent. population. The new data shows the number of 43 percent. population

There are three effective ways to stop COVID-19. First of all – restriction of free movement of people combined with aggressive testing – this way we could completely stop its transmission (but the virus is already present in practically all countries). Second – an effective, freely available vaccine, which is still not available. There is also a third way: there will be no one to get sick if we let the disease spread freely. Within a year or so, they will all be infected and gain the natural immunity so valued by vaccine opponents. Only a certain proportion of people will die (it may even be tens of millions worldwide), and immunity does not have to be permanent.

1. Work on the vaccine is accelerating. Human testing in July instead of September

Little is known about resistance to SARS-COV-2 virus: why is COVID-19 infection a minor infection for some and a deadly threat for others? Does having an infection give me permanent immunity – and how long does it last? Why do young people sometimes die from COVID-19, and sometimes they survive over 90 years?

The acquisition of immunity does not always mean complete protection against infection – in the case of influenza it is rather a significant reduction in the risk of contracting the disease, and when the disease develops – its course is milder. When we talk about resistance to COVID-19, we mainly mean antibodies to the SARS-CoV-2 virus. However, a few percent of those recovering from COVID-19 don’t produce them. These are mainly young people where white blood cells and cytokines have contributed to fighting the infection, rather than antibodies that neutralize the virus.

1. Why does the coronavirus kill some and run like a cold in others?

We still don’t know how long immunity to COVID-19 may last. This disease appeared at the end of last year. There are sporadic reports of the sick for the second time. We don’t know why this is so, but for other coronaviruses (for example, those that cause the common cold), immunity can only last for a few months. Over time, the amount of antibodies that your body makes to fight the disease the first time decreases. However, re-infection longer after being infected with COVID-19 is likely to be less severe. Such people cannot secrete as many viruses as before because the body can no longer reproduce the virus without restriction.

How long do antibodies stay in the body?

Experts previously noted that an infection that causes severe symptoms can lead to a stronger immune response and long-term immunity. Conversely, a mild or asymptomatic case may result in lower antibody levels.

The available immunological data come mainly from the sickest – those who have been hospitalized. However, most people have mild or no symptoms.

What is particularly worrying, a significant decrease in the amount of antibodies was observed in many patients within two months of recovery. Especially people who pass COVID-19 asymptomatically may be less immunized. A few weeks after recovery, 62,2 percent in the asymptomatic group. of people had short-term antibodies to the virus, and in the symptomatic group – 78,4%. In 8 weeks after recovery, the level of antibodies dropped in 81,1%. people from the asymptomatic group and in 62,2% of the symptomatic group. However, it is possible that this level of antibodies still protects against the disease. The differences in immunity between symptomatic and asymptomatic patients are not entirely clear – few asymptomatic individuals are tested. There is no exact definition of an asymptomatic person – is it a complete absence of symptoms or their slight severity?

1. The antibodies remain in the blood for about 3 months. Then we can get sick again?

We are still not sure what kind of immunity to COVID-19 we will get from vaccination: complete or simply protection against the worst symptoms. It cannot be judged by antibody levels; only Phase III trials, which directly measure vaccine efficacy, will provide an answer. This will better understand the relationship between antibody levels and immunity, and determine the type of immune response evoked needed to provide real protection.

If it turns out that prior exposure to COVID-19 does not guarantee permanent or strong immunity, the vaccine would need to be given to almost everyone. In this case, clinical trials to assess the safety and efficacy of the vaccine would need to include individuals from a previously infected population.

Herd immunity – we still don’t know everything about it

Group immunity, also known as ‘herd’ immunity, means that if enough people acquire immunity (either through a disease or through a vaccine), the virus stops spreading throughout the population without taking extra precautions. For years, vaccine opponents have used this phenomenon – they did not get vaccinated and did not get sick. However, a fleeting contact with a person infected with, for example, extremely contagious measles was enough to cause an epidemic in the clusters of unvaccinated people.

The development of herd immunity depends on many factors, not all of them exactly known.

First of all – on the virus reproduction rate (R0), i.e. the average number of people infected by a single infected person. To talk about epidemic extinction, the R-factor should be less than or equal to 1 – the lower the better. For example, for SARS-CoV-2 in Poland, RO is, according to the data of the Ministry of Health, on average 1,1, but in the Łódź Voivodeship it is currently 2,09, while in Warmińsko-Mazurskie – only 0,51. Perhaps the social life in Łódź is more lively, the residents do not like wearing masks? Or are they more susceptible to infection?

1. Why does Lodzkie have the highest coronavirus reproduction rate? Can it be explained?

Second – the number of infected. In Poland, it is over 35, in the world the number of confirmed cases exceeded 10 million. However, thirdly, scientists are wondering how many asymptomatic cases there are. It is still not known exactly because it is not physically possible to systematically test all of them. The Ministry of Health suspects that the percentage of unrecognized cases in Poland varies between 92 percent. and 98 percent If we assume that 98 percent are unrecognized. infections, the actual number would be 1 million 600 thousand.

If one infected infects two more people on average – then the number of infected grows exponentially. However, the more immunized people in the population, the more difficult it is to spread the disease. The easier the virus spreads, the more people should be immune to it in order to gain herd immunity. Measles is a particularly contagious disease (RO above 12), so about 90 percent must be immune. population.

A recent example of the emergence of herd immunity is the mosquito-borne microcephaly that causes microcephaly in the developing fetus, the Zika virus, whose 2015 epidemic caused a panic in Brazil. A 2017 study in one of the cities showed that more than 60 percent of them have already encountered the virus. inhabitants and the disease stopped spreading. Sanofi had to stop work on the vaccine – there was no demand for it anymore.

Earlier estimates by epidemiologists indicated that group immunity to SARS-CoV-2 appears with immunization of 60 percent. population. This would be the case with vaccinations that are equally accessible to everyone. However, the threshold of herd immunity is lower when that immunity comes from infection than when it comes from vaccination.

New calculations by mathematicians from the University of Nottingham and the University of Stockholm, published in Science, on immunity generated naturally as a result of exposure to the virus, take into account the age and social activity of people. With such assumptions, the group immunity threshold dropped to the more optimistic 43%. resistant people in the population. It was not age that turned out to be of key importance, but social activity. The more socially active a person is, the greater the risk of becoming infected – as well as infecting others. This is probably why in the USA an increasing proportion of those infected are young people, usually suffering from the infection asymptomatically.

The authors reserve that the value of 43 percent. indicative, but their research has potential implications for the current pandemic and the lifting of restrictions. They suggest that individual differences (e.g. in the level of activity) are an important element that must be incorporated into models for developing strategies to combat an epidemic.

Containment – not always gives immunity

Waiting for herd immunity to develop is not an acceptable solution – it takes too long, and even for COVID-19 killing one in a hundred people, it takes too many lives. Were it not for “flattening the curve”, the disease would have caused many more deaths, leading to the collapse of the healthcare system and paralysis of society. This was the case, for example, during the nineteenth-century epidemic of measles in Hawaii – everyone got sick at one time and 27 percent of them were ill. he died, unable to count on the help and care of others.

Given these dangers, the UK quickly pulled back from its originally promoted policy of “herd immunity”. Sweden still clings to it, despite numerous deaths, but neighboring countries have closed their borders.

1. What do Poles think about the Swedish strategy of fighting the virus? [LETTERS TO EDITOR]

However, in order for herd immunity to appear spontaneously, the disease must immunize for a sufficiently long time. To catch flu, the virus that mutates rapidly, requires repeated vaccinations every year. Having measles gives you life-long immunity, but it is better to get vaccinated because of possible complications. The incidence of rabies does not help, because 100% die. infected – therefore the only salvation is a vaccine, which in the case of this disease can, fortunately, be administered after exposure to the virus.

Hopefully, the available vaccines or effective treatments will arrive sooner than herd immunity, with millions of potential victims on a global scale. Taking simple precautions can reduce the loss of life. And it is not only about washing hands, masks or keeping distance. For example, loud music in bars makes their regulars speak loudly and move closer to each other. And that favors infection. (PAP)

Author: Paweł Wernicki