Summarize the facts about herd immunity

At least for a period of time 100 years old, “Herd immunity” breathed new life in 2020.

It starred in many headlines last month when reports of being a member of the White House Coronavirus Task Force surfaced. President’s advisor, Doctor. Scott Atlas, I recommend it as a strategy to fight COVID-19. The Washington Post reported Health policy experts from that Atlas Hoover Institution Researchers at Stanford University suggested that instead of trying to contain the virus through shutdown measures, the virus should be allowed to spread throughout the population in order to boost people’s immunity.

so Town hall event A few weeks later, President Donald Trump raised his thoughts, saying that the coronavirus simply “disappears” as people develop a “herd spirit.”

And just recently, Senator Rand Paul (R-Ky.) Last week. Caused a fierce debate At a committee hearing he suggested that the reduction in COVID cases in New York City was due to herd immunity or herd immunity, rather than public health measures such as wearing masks and social distance. Dr. Anthony Fauci, Chief Executive Officer of Infectious Diseases in the United States, accused Paul of noting that only 22% of the city’s population had COVID antibodies.

“If you believe that 22% is herd immunity, I believe you are one of them,” Forch told the Senator.

All this story made us think: People seem to be quite confused about herd immunity. What exactly does it mean and can it be used to fight COVID-19?

Costly and uncertain strategies

Herd immunity, also known as community immunity or herd immunity, refers to the fact that a sufficient number of people are well tolerated by the disease and the infectious pathogen is unlikely to spread from person to person. As a result, the entire community is protected, including those without immunity.

People generally acquire immunity by either vaccination or infection. For most diseases in recent history, from smallpox and polio to diphtheria and rubella, vaccines have been the path to herd immunity. For the most contagious diseases such as measles, about 94% of the population needs to be vaccinated to achieve that level of protection. For COVID-19, scientists estimate that percentage is between 50% and 70%.

Prior to the COVID pandemic, experts cannot recall an example of the government deliberately turning to natural infections to achieve herd immunity. Dr. Carlos Del Rio, an infectious disease and vaccine expert at Emory University School of Medicine, said that in general, such strategies can lead to widespread illness and death.

“That’s a terrible idea,” Del Rio said. “It basically gives up on public health.”

A New large-scale research It was found that less than 1 in 10 Americans have antibodies to SARS-CoV-2, the virus that causes COVID-19. Even in the most devastated areas, such as New York City, the estimated immunity of the population is about 25%.

Josh Mishaw, Associate Director of KFF’s Global Health Policy, says that reaching 50% to 70% immunity means “an incredible number of deaths”, about four times that of infected people. Even those who survive can have serious effects on the heart, brain, and other organs, leaving lifelong damage. (KHN is an editorial independent program of KFF.)

“Unless your goal is to pursue suffering and death, it’s not a strategy to pursue,” Mishaw said.

In addition, some scientists say that innate immunity may not even be feasible with COVID-19.Most people will have some protection once infected, but will recover from the disease. Reinfection He raised questions about how long innate immunity lasts and whether those with immunity can still spread the virus.

Dr. Stuartley, an infectious disease expert at Johns Hopkins University, said who is protected from COVID-19 even with the method scientists use to measure immunity (a blood test that detects antibodies to the coronavirus). He said it may not be an exact indication of what is happening. Of medicine.

With so many unanswered questions, he concludes: “Natural herd immunity cannot be relied on as a way to control this epidemic.”

Vaccines, on the other hand, can be made to elicit stronger immunity than natural infections, Ray said. So, for example, people infected with spontaneous tetanus are advised to get the tetanus vaccine. Vaccines being developed for COVID-19 are expected to provide the same high levels of immunity.

But what about Sweden?

In the political debate over COVID-19, proponents of the natural herd immunity strategy often point to Sweden as a model. The Scandinavian country has imposed fewer economic closures, but its mortality rate is lower than that of the United States, Paul said in a Senate hearing Wednesday.

However, health experts, including Fouch during the same hearing, claim that it is a flawed comparison. Dr. John Andras, an epidemiologist at the George Washington University Milken Institute School of Public Health, said that the population of the United States is much more diverse and vulnerable groups such as blacks and Hispanic Americans disproportionate the effects of the coronavirus. He said he was receiving it. He said the United States is also densely populated, especially in the coastal areas.

Compared to other Scandinavian countries, Sweden has a much higher death toll. According to the report, 5,880 people have died in connection with COVID-19 so far. Data from Johns Hopkins University.. This is about 58 deaths per 100,000 inhabitants, several times the mortality rate of 5 or 6 per 100,000 in Norway and Finland.In fact, as a result of COVID-19, Sweden Record the highest number of deaths Because famine struck the country 150 years ago.And The number of cases is increasing..

Despite that level of loss, it is still unclear whether Sweden has reached the herd immunity threshold.By late April, according to a national public health agency survey Only 7% of residents In Stockholm, there was an antibody against COVID-19. In other Swedish cities, the proportion was even lower.

The results of these findings reflect other studies around the world. Researchers have found in several cities in Spain, Switzerland and the United States, with the exception of New York City. Less than 10% Despite months of exposure and high infection rates, the population had COVID-19 antibodies by June.The results led to commentators on The Lancet, a medical research journal. write“In light of these findings, the approach proposed to achieve herd immunity through natural infections is not only very unethical, but also unattainable.”

Herd immunity is still far away

The bottom line, according to medical experts, is that natural herd immunity is an uncertain strategy, and trying to pursue it can lead to many unnecessary deaths. When vaccines become available, they provide a safer route to protect the entire community.

Until then, they emphasize that there is still much work to be done to counter the pandemic. Wearing masks, practicing social distance, washing hands, strengthening tests, and contact tracing have all proven to help control the spread of the virus.

“While waiting for new tools to be added to the toolbox, we must continue to remind ourselves that there is a workaround at this moment that can be used to save lives,” Andras said. It was.

KHN reporter Victoria Knight contributed to this article.