Group immunity to COVID-19 won't come until 2022 according to Harvard: we'll have to get used to social distance

If we set a great goal in the fight against the COVID-19 pandemic, it would be group impunity. This occurs with acquired immunity and by vaccinating, providing indirect protection to unvaccinated individuals. When will it happen with COVID-19?

It seems that we will have to wait, at least this is what an important study carried out by Harvard University states, which explains by means of a powerful mathematical model how long it will take to stabilize infections. The most realistic date, they claim, will be July 2022.

Group immunity against COVID-19: what you need to know

We have already told you on other occasions how it works. In a nutshell, once a population is immunized, once the population is immunized, the virus cannot continue to spread because the immunization (of the group) acts as a barrier, protecting those who have not had the disease.

The effectiveness of vaccines lies precisely in this key: group immunity offers an automatic limitation to the spread of disease. This is important to protect population groups that cannot be vaccinated, such as children or immunosuppressed people. In the case of COVID-19, with the immense infectious capacity it has, this is a key factor.

Group immunity cannot be understood as a kind of magic number from which a disease is controlled or there are no new infected. Statistically speaking, we do know that when a disease spreads to a person or less from a patient (R0 of one or less), contagions disappear over time. This gives us some assurance to say that once a percentage of people immunized has been reached, the peaks of epidemics no longer occur, so the ravages of diseases can be mitigated. The other option, when group immunity is not available, is social distancing to avoid contacts. This can be done more or less strictly, going from total confinement to lighter measures, such as reducing mass events or the use of mandatory protective material.

The immunization figure that is usually considered for diseases with an R0 of more than one is usually 70% of the vaccinated population. For highly infectious diseases, such as polio, the percentage can reach 90%. Measles, with an R0 between 12 and 18, the figure reaches 99%. And what is that percentage for COVID-19? Like other diseases with an R0 of almost 6, the percentage will vary between 50 and 70%, although this can only be known with complete certainty when we have analyzed all the global data, after controlling for the pandemic.

A model to know when we will be immunized

The good thing about models is that they can quickly and accurately adapt to new situations. The same has happened with the model developed by Harvard's Department of Immunology and Infectious Diseases. Biostatistics experts had already worked with other diseases such as SARS or MERS, first cousins ​​of COVID-19.

Thanks to this, it has not been difficult to design a new model that collects information from more than 95% of the United States. This allows researchers to play around with data on the expansion of the coronavirus and compare it with the rest of the world. Using and adjusting the mathematical model, they have determined several dozen possible scenarios that cover all kinds of situations.

In fact, it is the most accurate model published to date and even considers the possibility of infected people being reinfected or not achieving immunity. They also consider the possibility of a mutation that accelerates the viralization process and even estimates of what would happen if we did not impose the social distance (something that other models from the University of Chicago, from the University of Soonsil, in South Korea, have already foreseen, or at Cornell University, in Australia, to give some examples, and they coincide).

The result, the researchers explain, is clear: the most realistic case is that we will have to continue adopting social distancing measures until July 2022.For what reason? According to the calculations of these models, we will not be able to reduce the contagion capacity to one or less until these dates due to the progression of immunization and the rate at which vaccines will appear.

Big questions about immunization

From the early stages of the pandemic, it has been discussed whether or not patients are capable of reinfection. Viruses have the ability to mutate rapidly. SARS-CoV-2 is completely new, so there is no population immunity. In the absence of it, it is much easier for us to pass the disease and re-infect ourselves in a short time due to another strain or for reasons that are still unknown.

On the other hand, we know that the first vaccines will start to arrive in the autumn in the best case, but it will probably not be until the middle of next year that they will be distributed in a general way and, as the model points out, they will not reach the enough population until 2022. In summary: statistics indicate that it is unlikely that we will be able to achieve group immunity that stabilizes the disease until the middle of July 2022. To avoid contagions, we will have to resort to the substitute for such immunity: social distancing. .

And why not let COVID-19 infect almost the entire population, instead of confining ourselves and taking action? In diseases like the cold, the solution is to let it evolve and stabilize quickly. But with a disease whose mortality reaches 14% in the most severe cases, this option is not valid.

By now, based on the data we have, and while we may still have to wait a bit to better understand COVID-19, it is clear that it will take years to obtain group immunity and vaccines to help us expand and effects of the disease, stabilize.

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