“When will the pandemic end?” The answer to the question is actually "When will we reach herd immunity?" same as the answer to the question. There is an immunity threshold value that we do not know yet about the goal of achieving social herd immunity. It is perhaps impossible to reach this threshold. Although herd immunity (immunity through vaccination and/or disease) is the long-term, not-so-imminent, promised end of the pandemic, its requirements are quite specific. But still, vaccines can help us end the pandemic.

Technically, it means herd immunity; means reaching the probability that a sick person will infect less than 1 person on average. Patient zero means that even if patient zero infects another person, the second person does not infect a third. This is exactly what happened historically with measles and polio. Of course, vaccines did that.

The herd immunity threshold for Covid-19 disease is estimated to be between 60% and 90%. This ratio shows the proportion of the population that has acquired immunity through disease or vaccination.

However, in the light of the latest information, it seems that we will not be able to achieve herd immunity in the near future.

Although the covid-19 vaccines have been successful beyond expectations, we see that they cannot completely reset the spread of the virus. As long as the spread of the virus is not stopped, we see that herd immunity is becoming an increasingly difficult target. Although vaccines have been very successful in alleviating disease, reducing hospitalization rates and deaths, transmission must also be significantly reduced for herd immunity to occur. If we fail to increase the vaccine's ability to prevent transmission of the virus above the herd immunity threshold, vaccination of 100% of the population remains the only criterion necessary for herd immunity. That means impossible.

At the moment, there is a serious rate in Turkey saying that no matter what happens, it will not be vaccinated. Unfortunately, this raises our herd immunity threshold even higher. Our expectation from Covid-19 vaccines is no longer that it completely wipes out the disease from the face of the earth. Rather, as in the flu vaccines, asymptomatic or mild illness, hospitalization and death rates are reduced to almost zero.

The virus is circulating more than last year. But far fewer people are dying now. We owe this to vaccines.

It also ensures less transmission of the virus, regardless of the vaccines. As the viral load that can cling to the body is less, the number of contagious viruses scattered around decreases. This too. means fewer people are exposed to the virus and fewer people get sick or die.

There will probably be no such thing as "zero covid-19 cases". A global reset of the virus is an elusive dream. But living with the coronavirus is becoming much more normal, and it will come.

One of the biggest obstacles to herd immunity is the variants of the virus. As the virus evolves, our vaccines and immunities need to keep up with new forms of the virus.

This entire process also needs to run simultaneously globally. Rich countries have now bought most of the world's vaccine stock. Even if they have vaccinated a large part of their own population by the end of 2021, the virus will still be circulating elsewhere in the world. In this case, it will continue to evolve and create new variants. The new variants will be less and less effective than the vaccines we currently use, and the virus will return to rich countries in new variants, much stronger than before. In other words, rich countries are stockpiling vaccines against themselves. It will be a never-ending race, although vaccines will be updated against new variants.

We can collect the community immunity that will be formed thanks to vaccines in 4 main thresholds, from the easiest to the most difficult.

First threshold, relief of severe symptoms of the disease (hospitalization and death)

The second threshold is the elimination of mild symptoms of the disease (symptoms of a cold)

The third threshold is the prevention of transmission of the disease to others.

The fourth threshold, the end of being infected with the disease

The first and second thresholds at which vaccines are most effective. Hospitalizations and deaths have decreased drastically thanks to the vaccine. Many vaccinated people go through the disease asymptomatically. But vaccines are not that effective at preventing the transmission of the disease yet.

There is a biological explanation for this situation: The region where immunity occurs is very important. Respiratory viruses, such as coronavirus, first take hold in the human body through the nose and throat. Current covid-19 vaccines are applied to the arm muscles. With this application, the body's immune system gives a strong immune response and produces high levels of antibodies (titers) in the blood. But antibodies in the nasal and throat mucosa, our first line of defense against coronavirus, are not as strong as those in the blood. As time passes, regional antibodies in the upper respiratory tract gradually decrease. However, since the protection in the lungs, which is the lower respiratory tract, remains high for a long time, severe infections such as pneumonia are prevented.

So what does all this mean for the future of covid-19? One possible scenario is that the disease produces symptoms of the common cold in humans, but not a serious infection, much like the four previous types of coronavirus have followed so far. Even though ordinary cold coronaviruses can be transmitted to humans repeatedly, we are having fewer and fewer symptoms because of the immunity we have developed over time. Therefore, according to the optimistic forecast, covid-19 infections will gradually lose their effect, although they continue. In fact, a scientific view is that a type of coronavirus was born with the pandemic in 1889, but now it is in the class of ordinary cold diseases.

It seems that little by little, children will start to be vaccinated, because we know that although it affects children much more than the elderly, it still has more devastating effects for children than the flu virus. Vaccination of children will further reduce the spread of the virus.

Although it seems impossible to reach the herd immunity level in the near future; Each vaccinated person sheds less virus than an unvaccinated person. A person who is exposed to the virus less often falls ill, is hospitalized less often, or dies.