COVID-19 in Vaccinated People. These factors increase the risk of a breakthrough infection

Scientists and doctors have long talked about the fact that it is possible to get COVID-19 despite receiving two vaccines against the disease. However, many people who struggle with the coronavirus despite undergoing a primary vaccination course (two doses) wonder how they got infected and why they turned out to be less resistant to SARS-CoV-2 than others. The answer to this question is provided by the latest publication in the scientific journal “Nature Reviews Immunology”. The most important findings of its authors are presented below.

1. It is possible to get COVID-10 after two doses of vaccination against the disease. We are then talking about the so-called breakthrough infection
2. The vaccine does not protect 100%. against infection, and above all reduces the risk of severe course and death caused by it
3. What is the risk of getting an infection while still being vaccinated? An American-Israeli team of scientists has just published the results of the study
4. More information can be found on the Onet homepage

Reasons for getting COVID-19 despite vaccination

The most important questions that arise in the context of the effectiveness of vaccination against COVID-19 relate to factors that we do not have much influence on: the duration of protection provided by the vaccine and resistance to new variants of the coronavirus. How do these rates decrease over time since the end of the primary vaccination course and the emergence of new SARS-CoV-2 mutations? In short, why do vaccinated people get COVID-19?

According to the authors of the Nature Reviews Immunology article, several factors influence the incidence of vaccinated people.

The more people vaccinated, the more COVID-19 in this group

The first is fairly obvious – there are more and more people among us who have either taken at least one dose of the COVID-10 vaccine or have undergone a complete primary immunization course. If society reaches a high vaccination rate, it is natural that most infections will occur in those who are vaccinated.

This is the case in Ireland, for example, where 93,3% are fully vaccinated. adult citizens (one dose was taken by 94,5% of them), which means 76,6% of the total population. It should come as no surprise, then, that both the number of infections and deaths of vaccinated people in this country is higher than that of unvaccinated people.

1. Also read: More and more vaccinated in hospitals. There are two main reasons

The immune response diminishes over time

The second reason for a breakthrough infection is the inadequate immune response of the vaccinated person exposed to the SARS-CoV-2 virus carrier. The degree of protection that vaccines offer may diminish over time, so the immune response may not be sufficient to stop or quickly control the infection. Importantly, however, such protection may also increase, both after a breakthrough infection and after the next dose of the vaccine.

The effectiveness of vaccines varies

The third factor that increases the risk of developing COVID-19 despite vaccination is the different efficacy of vaccines, especially for certain groups of patients. These are mainly people with various diseases that lower general immunity, e.g. those with haematological cancers (there is evidence that among those vaccinated with such diseases, higher rates of SARS-CoV-2 and / or severe COVID-19 infection are reported).

«Measuring the effectiveness of a vaccine is difficult for several reasons. Given the high burden of infection before vaccines became available, some people who are not vaccinated will nevertheless have some immunity as a result of prior infection, complicating comparisons of immunity between these groups »the researchers note.

1. See also: Vaccine effectiveness declines over time. In one of them, the decline is drastic

New variants of the coronavirus and vaccine effectiveness

The fourth cause of a breakthrough infection is, of course, exposure to a new genetic variant of the virus. Some studies suggest that the likelihood of a breakthrough infection is higher with the Delta variant than with the Alpha variant. However, the researchers point out that such comparisons are extremely difficult as in most countries the two variants coexisted for a short time, which made longer comparative studies impossible.

1. See also: Delta and Omikron compared. Scientists point to the most important differences

The question remains, which of these factors is most important for a breakthrough infection? The researchers say it is likely that “the degree of protection depends on the strength of the immune system at the time a person is exposed”. (This model suggests that age determines a lower peak response, time decreases the immune response, and this varies with virus variants.

Breakthrough infection and severe COVID-19 course

The article in Nature Reviews Immunology also reported that breakthrough infection sometimes develops into a severe disease in vaccinated people. The research of the authors of the publication shows that the severe course indicator is not common, however, such cases do occur despite vaccination. Who can they concern?

Researchers from Israel have investigated this issue, where COVID-19 cases have increased sharply this summer, despite the high vaccination coverage rate. Most of the documented severe COVID-19 cases there were in people vaccinated with two doses of the Pfizer vaccine. The fact that they occurred at a time when most of the age groups at the highest risk were five months (or more) after receiving the second dose of the vaccine prompted the country to introduce a third dose of the vaccine. As a result, it drastically reduced the incidence of severe COVID-19 in people who received the booster, and in different age groups.

1. How many people got infected after taking the third dose? Data from Israel

The Lancet Microbe sheds a different light on the seriousness of SARS-CoV-2 infection. One of the articles presents the results of a study of a group of vaccinated people who became infected with the Delta variant, and their disease was severe. Its authors came to three important conclusions.

First, the mean age of the severely vaccinated COVID-19 population was higher than the mean age of the unvaccinated (71,5 vs 55,2 years). Second, those who were vaccinated experienced fewer complications than those who did not receive the vaccine. And third, their hospitalization time was shorter than that of the unvaccinated.

How many people have COVID-19 after vaccination?

The Polish Ministry of Health does not regularly publish data on the incidence of COVID-19 among vaccinated people. However, according to the latest information (December 3), fully vaccinated people account for 1,41 percent. all infected. «From the moment of starting vaccination with the second dose of 13,5 percent. infections were fully vaccinated, the ministry said.

The editorial board recommends:

1. Which vaccine for the third dose? What combination is the most effective?
2. What happens after the third dose of the COVID-19 vaccine?
3. How to sign up for a third dose of COVID-19 vaccine? [WE EXPLAIN]
4. Are you going for the third dose? Check with what preparation you will be vaccinated

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