Why herd immunity does not work

The problem is that, as more people are vaccinated, they will increase their interactions, and that changes the herd-immunity equation, which relies in part on how many people are being exposed to the virus. Scientists race to find answers. Non-pharmaceutical interventions will continue to play a crucial part in keeping cases down, Del Valle says. The whole point is to break the transmission path, she says, and limiting social contact and continuing protective behaviours such as masking can help to reduce the spread of new variants while vaccines are rolling out.

Texas and some other US state governments are already lifting mask mandates, even though substantial proportions of their populations remain unprotected. Even after the threshold has been passed, isolated outbreaks will still occur. To understand the additive effects of behaviour and immunity, consider that this flu season has been unusually mild. This back-of-the-envelope calculation shows how behaviour can change the equation, and why more people would need to be immunized to attain herd immunity as people stop practising behaviours such as social distancing.

Ending transmission of the virus is one way to return to normal. Even without herd immunity, the ability to vaccinate vulnerable people seems to be reducing hospitalizations and deaths from COVID The disease might not disappear any time soon, but its prominence is likely to wane.

News 11 NOV Career Guide 10 NOV Article 10 NOV News 04 NOV News Explainer 02 NOV Francis Crick Institute. It varies from disease to disease. The more contagious a disease is, the greater the proportion of the population that needs to be immune to the disease to stop its spread.

For example, the measles is a highly contagious illness. Herd immunity can be reached when enough people in the population have recovered from a disease and have developed protective antibodies against future infection. However, there are some major problems with relying on community infection to create herd immunity to the virus that causes COVID :. Herd immunity also can be reached when enough people have been vaccinated against a disease and have developed protective antibodies against future infection.

Unlike the natural infection method, vaccines create immunity without causing illness or resulting complications. Using the concept of herd immunity, vaccines have successfully controlled contagious diseases such as smallpox, polio, diphtheria, rubella and many others. Herd immunity makes it possible to protect the population from a disease, including those who can't be vaccinated, such as newborns or those who have compromised immune systems.

The U. For example:. The number of fully vaccinated adults continues to rise. In addition, more than 31 million people in the U. However, if you are in an area with a high number of new COVID cases in the last week, the CDC recommends wearing a mask indoors in public and outdoors in crowded areas or when you are in close contact with unvaccinated people.

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A single copy of these materials may be reprinted for noncommercial personal use only. Depending on the virus, you can become immune—or resistant—to it if you develop antibodies to it. Wohl says. This results in the whole community becoming protected—not just those who are immune. Herd immunity can protect people who cannot be vaccinated and those with compromised immune systems who are most vulnerable to serious illness.

However, viruses are not created equally. Unfortunately, this provides fertile ground for ongoing evolution of the virus. No country is going to lock its borders perpetually. This means the entire global population needs to reach the same sort of threshold round about the same time. This will require ensuring that we get the majority of individuals, especially adults, and particularly those at a higher risk of developing severe COVID and dying, vaccinated as quickly as possible.

In my view this could be achieved in South Africa with 20 million people vaccinated — not the 40 million target set by the government. If South Africa achieved this milestone, it could get back to a relatively normal lifestyle even with the virus continuing to circulate and causing the occasional outbreak. We are simply going to have to become comfortable with the idea that SARS-CoV-2 is going to be like one of the numerous other viruses that circulate that cause respiratory illness each day.

Usually mild infections, and less often a severe disease. A major advance would be for COVID to be no more severe than what is seen every influenza season 10, to 11, deaths in South Africa.

The UK experience is where we should be heading.