Herd immunity seems unlikely for COVID-19, but CDC says vaccinated people can drop masks in most configurations


Wwhen COVID-19 began to spread, public health and medical experts began talking about the need for the United States to achieve herd immunity to stop the spread of coronavirus. Experts have estimated that between 60% and 90% of people in the US should be vaccinated for this to happen. Only approximately 35% of the population has been completely vaccinatedand yet the CDC said on May 14, 2021 that fully vaccinated people can lose the mask in most indoor and outdoor settings.

Now an important question arises: what if we don’t get the herd’s immunity? Dr. William Petri is a professor of infectious diseases at the University of Virginia who helps lead the global program to achieve immunity from the polio herd as chairman of the World Health Organization’s polio research committee. Here he answers questions about herd immunity and COVID-19.

What is herd immunity?

Herd immunity occurs when there are enough people immunized in a population to stop new infections. It means that there are enough people who have achieved immunity to interrupt person-to-person transmission in the community, thus protecting non-immune people.

Immunity can result from vaccination or previous infection. Herd immunity can exist worldwide, as with smallpox, or in a country or region. For example, the US and many other countries they have achieved herd immunity against polio and measles, although global herd immunity does not yet exist.

Has herd immunity been achieved globally for other infections?

This has only happened once on a global scale, with smallpox eradication in 1980. This happened after an intensive vaccination campaign around the world for a decade.

We are also approaching the global immunity of the herd against polio. When the Global Initiative for the Eradication of Poliomyelitis formed in 1988, there were 125 countries with endemic poliomyelitis and more than 300,000 children paralyzed annually. Today, after 33 years of vaccination campaigns, Afghanistan and Pakistan are the only countries with wild polio virus two cases of paralysis due to wild poliovirus this year. Thus, the immunity of the herd can be achieved worldwide, but only through extraordinary efforts with global collaboration.

It seems that the target sites for herd immunity continue to change. Because?

Experts estimate that between 60% and 90% of the American population it should be immune so that there is immunity in the herd. This wide range is due to the fact that there are many moving parts that determine what is needed to achieve the herd’s immunity.

Factors influencing whether the target is 60% or 90% include how vaccination and previous infection prevent not only diseases due to COVID-19, but also infection and transmission to COVID-19. other people. Some additional considerations include the increased transmissibility of new SARS-CoV-2 variants and the use of measures to interrupt transmission, including face masks and social distancing. Other important factors include the duration of immunity after vaccination or infection and environmental factors such as seasonality, population size, and density and heterogeneity within populations in immunity.

What is the biggest barrier to herd immunity in the US?

Two factors could lead to the failure to achieve sufficiently high levels of immunity: not all adults receive the vaccine because of the “vaccination of the vaccine” and the likely need to vaccinate adolescents and children. The FDA authorized the emergency use of the Pfizer-BioNTech COVID-19 vaccine for teens ages 12-15 on May 10, 2021, so that might help. But an additional barrier is the constant pressure to reintroduce the infection from other countries where vaccination is not as readily available as in the US.

Therefore, achieving herd immunity to the point of completely blocking new infections is a laudable goal, but not easily achievable. I believe that for COVID-19 at this time, it will only be possible with the concerted global effort for years, similar to the one that led to the eradication of smallpox.

Why are there people who are hesitant about the vaccine?

People may be hesitant about the vaccine for a variety of reasons, such as a lack of confidence in the vaccine, the discomfort of receiving the vaccine, or complacency. thinking that if they get COVID-19 it won’t be serious.

Lack of trust includes concerns about vaccine safety or skepticism about health care providers and the public health officials who administer them. Complacency reflects a personal decision that vaccination is not a priority for that individual because he or she perceives that the infection is not serious or because of temporary skills. Comfort issues include availability and complexity, such as having to take two doses.

Since the immunity of the flock will not be achieved, what will our life be like?

At least until 2022 and probably for much longer, I don’t expect any immunity for the COVID-19 herd. What will be there, probably later this summer in the US, is a new normal. There will be far fewer cases and deaths due to COVID-19, and social alienation and masking will be eliminated throughout the year, as evidenced by the new CDC guidelines published on May 13, 2021, which vaccinated people should not wear masks in most places.

But there will be a seasonality of coronavirus infections. This means that there will be fewer in the summer and more in the winter. We will also see outbreaks in regions and subgroups of the population that do not have adequate immunity, blockades of cities or regions of short duration, new more transmissible variants and a likely requirement for vaccine booster vaccines. We cannot disappoint in the research and development of new treatments and vaccines, as studies show COVID-19 is here to stay.

William Petri, Professor of Medicine, University of Virginia

This article is republished from The conversation under a Creative Commons license. Read the original article.

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