It is the season of the year-end list. Typically, Vox’s science team has some fun and compiles a year-end list of bad health and science ideas that should die by the end of the year. In the past, we focused on homeopathic medicine, declared that it was time to end the relevance of the fatally defective Stanford prison experiment, and dispelled the myths about climate change. This year, however, we have only one goal for intellectual demolition.
With the end of 2020, we will leave behind the idea of using the collective immunity acquired by natural infections as a way to fight the Covid-19 pandemic. Too many words to describe a simple and terrible idea: that we could end the pandemic sooner if more people – particularly young people, people at lower risk – get infected with the coronavirus and develop immunity as a result.
In response to a pandemic, the idea is unprecedented. “Never in the history of public health has collective immunity been used as a strategy to respond to an outbreak, let alone a pandemic,” said World Health Organization Director-General Tedros Adhanom Ghebreyesus in October. “It is scientifically and ethically problematic.”
And yet it dominated – in the White House, in particular.
Former White House adviser Scott Atlas (who is a neuroradiologist, not an epidemiologist) was particularly vehement about seeking more infections. “When younger, healthier people are infected, that’s good,” Atlas said in a July interview with the San Diego news station KUSI-TV. “The goal is not to eliminate all cases. This is not rational, it is not necessary if we only protect people who will have serious complications. “
Let us be clear, it is not “good” when young people get sick. On the one hand, some of these young people can die, others can become seriously ill and a proportion still not understood can suffer long-term consequences. The more people infected, the more likely that rare and horrible things will happen, such as a swelling in the brain of a 4-month-old baby after a positive Covid-19 test. For this reason, among others, trying to keep infections only for young people or people at low risk is a reckless game.
Why increasing herd immunity through natural infections is a bad idea
There is an almost understandable case to explain why some people would press for a collective immunity strategy. We are isolated from those we care about, business is suffering, education has been damaged and so is our mental health. What if we could just go back to some parts of normal life and contain the risks for those who are less likely to get hurt?
That thought proved to be reckless. Sweden, a country that sought a more permissive strategy with regard to social distance, has the highest Covid-19 mortality rate in Europe.
And look what happened in Manaus, Brazil: the city of about 2 million people experienced one of the most serious and uncontrolled Covid-19 outbreaks in the world. The researchers now estimate that between 44 and 66 percent of the city’s population has been infected with the virus, meaning that it is possible that collective immunity has been achieved there (another estimate pointed to an infection rate of 76 percent). But during the epidemic period, there were four times more deaths than normal in Manaus for that period of the year.
More typically, the term “herd immunity” is referred to in the context of vaccination campaigns against contagious viruses such as measles. The concept helps public health officials to think through how many people in a population need to be vaccinated to prevent outbreaks. It should not be applied to control a pandemic due to natural infection. Here are five reasons:
- Even if we could limit exposure to people less likely to die from Covid-19, that group can still suffer immense consequences from the infection – such as hospitalization, long-term symptoms, organ damage, missing work, high medical bills and yes, death.
- Herd immunity is a very high barrier to natural infections. There is no single, perfect estimate of what percentage of the United States’ population has already been infected with the virus. But by all accounts, it is far from the number needed for collective immunity to take action. The CDC now estimates that there have been 91 million SARS-CoV-2 infections in the United States – about 27 percent of the population (although this can be an overestimate) About 60% of the population would be needed to obtain collective immunity. This is an approximate guess; it can be bigger. So, we’re halfway there. Who wants to double the destruction already caused by this virus? In the United States, more than 330,000 people died. (In addition, collective immunity does not work nationally, but on a community-by-community basis. In other words, some communities are still much more vulnerable than others.)
- Scientists do not know how long the naturally acquired immunity to the virus lasts, or how common reinfections can be. If immunity decreases and the rate of reinfection is high, it will be even more difficult to develop collective immunity.
- By allowing the pandemic to spread, we run the risk of exceeding the herd’s immunity limit. After reaching the herd’s immunity limit, this does not mean that the pandemic is over. “This means that, on average, each infection causes less than one continuous infection,” said Harvard epidemiologist Bill Hanage. “This is of limited use if you already have a million people infected.” If each infection causes an average of 0.8 new infections, the epidemic will subside. But 0.8 is not zero. If a million people are infected by the time collective immunity is achieved, according to the example of Hanage, those already infected can infect another 800,000.
- A herd immunity strategy is likely to harm some groups more than others. There are several reasons why someone may have a serious case of Covid-19. It’s not just about age – conditions like diabetes and hypertension also increase your risk. The same is true of social factors, including poverty, working conditions and incarceration.
In the USA, the serious deaths of Covid-19 disproportionately affected minorities and disadvantaged populations. Encouraging collective immunity through coronavirus infections risks further isolating these already marginalized communities from society, since they may not feel safe in a more relaxed environment. Or, even worse, we risk sacrificing your health in the name of reaching a level of population immunity sufficient to control the virus.
Soon, collective immunity will be a good thing – because of the vaccines
Fortunately, we now have a way to develop herd immunity without the risks posed by infections: vaccines. Unlike the immunity conferred by a real viral infection, the immunity obtained through the vaccine does not carry the cost of illness and death. Vaccines are safe. And although they don’t turn the pandemic overnight, they will help to end it.
We still have to make a difficult wait. The launch of vaccines will be slow. Throughout 2020, “herd immunity” was used as an abbreviation for “let the pandemic spread”. There was also persistent and erroneous positive thinking for some who said that collective immunity had already been achieved, or it could be achieved earlier than scientists say, or it could be achieved without incurring horrible losses. Yes, the economic constraints of the pandemic were, and still are, painful. But it is also true: the government could have done more to help.
Soon, collective immunity will become good news as we move towards it collectively – and safely – through vaccines. As vaccines are distributed, herd immunity will develop in a controlled and ethical manner. The pandemic will decrease.
And in doing so, let us not forget: the calls to increase the herd’s immunity through infections were a terrible idea. We will not repeat them in the future.