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Why can no vaccine be 100 percent effective?

The new vaccines against the corona virus are expected to provide 70-90 percent protection.

Is it good enough to eradicate a global epidemic?

And when will we know if the corona vaccines really work?

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• Vaccine for corona

• Vaccine

• Corona

• covid-19

Leahy root

Sunday, 06 December 2020, 00:00

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In the video: The British Minister of Health expresses satisfaction with the approval for the use of the Pfizer vaccine (Photo: Reuters, edited by Tal Reznik)

The announcement that there is not one, but three corona virus vaccines that can be used very soon, was initially welcomed, and then quite astonishing, thanks to the success rates published by the companies that are in the race.

The results of the clinical trials on the three vaccines show that their effectiveness - that is, how well they prevent people from getting corona - is between 62 percent and 95 percent.

But should the fact that none of them have reported 100 percent success be embarrassing for these companies?

The truth is that no vaccine reaches one hundred percent success.

In fact, experts believe that the new vaccines against the corona virus may provide better protection than many other vaccines, since 70-90 percent efficacy is considered very high.

Just for comparison the vaccine that the flu virus currently has stands at about 60 percent efficacy.

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To maintain high efficacy rates, the two leading Pfizer and Modernena vaccines are given in two doses.

The first is called priming - a stage of initial introduction of the virus.

Then the second dose causes the immune system to produce a very focused, strong response and is able to hold for a long time (similar to the flu vaccine which is also given in two doses the first time given to children).

Efficiency of 70-90 percent.

The four leading corona vaccines: Moderna, Pfizer, Astra-Zenika and Sputnik V Russian (Illustration: Official Websites, Walla! NEWS System)

In the case of the corona virus, it is too early to assess whether the vaccine will completely prevent infection with the corona or will only prevent a serious illness and even for how long it will be effective, if at all.

Or in the worst case - will the vaccine be able to increase the disease.

Why then can a vaccine not offer complete protection?

Vaccines work by creating a kind of memory of the disease, so that in case the immune system comes in contact with it again - it will recognize the disease and trigger a significant and stronger response.

Which means the virus will have no chance of causing disease and symptoms.

One hundred percent effective vaccination can be the goal, but in reality such results cannot be achieved, and there are several reasons for this.

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"The immune system is very variable. There are a lot of factors because it is a super complex system," explains Anar Otolangi, a doctoral student in immunology at Ben-Gurion and a member of the Mada'at Association. It is a part of the genome that varies greatly from person to person, this is one of the reasons why it is difficult to find bone marrow donors, for example. "

According to Otolengi, the immune system behaves a little differently in every other person and therefore people will not always respond to the vaccine in the same way.

It is important to understand that the variance in the immune system also stems from our lifestyle and the environment in which we live.

For example, overweight people who develop inflammation in the body may have weaker immunity, or older people whose immune systems are weaker, so some of the vaccines they receive have components that increase the immune system's response.

Only after millions have been vaccinated will we get answers to some of the questions.

Participant in Pfizer trial gets vaccinated for corona in Maryland, USA (Photo: Reuters)

A second reason has to do with scientists' desire to control the vaccine.

"With the years and the development of technology, we want to control and monitor the process, so we are producing more and more vaccines that have fewer antigens that are part of the bacterium or virus or other foreign factor to which the immune system responds. To increase control and reduce side effects The antigens, "Otolangi explains.

An example of this can be seen in the corona vaccine in which only the spike protein is injected.

"It could be that because of the differences in the immune system, people will be able to produce immunity to another protein and not to the spike protein, which will impair the effectiveness of the vaccine in some of them."

It is possible to get the vaccine and not develop immunity

The third reason has to do with the random behavior of the immune system.

"It's a system based on encounters that has a certain probability that they will happen, but they don't always happen. That means you can get the vaccine, and in case you don't develop immunity to it."

As an example he gives the measles vaccine whose effectiveness in the first dose is 95 percent, and in the second dose they already rise to 97-99 percent, and it is a vaccine that when it works, it gives the vaccine immunity for life.

Why not the other percentages?

Not clear, says Otolengi.

As mentioned, it is too early to talk about the effectiveness of corona vaccines and only after millions have been vaccinated can we get answers to some of the troubling questions we still have regarding these vaccines.

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