Shepherding the Herd | When It’s Too Dangerous to Rely on Protection by the Immunity of Others

The Austrian government has dealt with COVID-19 based on lessons learned from our Italian neighbors and the ski resort coronavirus hotspots. So far, anything else is simply too dangerous.

These days there is a lot of talk about herd immunity, mainly because people are itching to get back to normal life, compromised livelihoods of many people, and the tanking of the economy. Herd immunity for us means that when enough people in Austria have had COVID-19 and develop immunity that protects them against reinfection, the rate of virus spread slows down.

So far, the Austrian government dealt with COVID-19 based on lessons learned from our Italian neighbors and the ski resort coronavirus hotspots. In his press conference on March 13th, 2020, Sebastian Kurz pleaded with Austrians to protect their parents and grandparents by isolating themselves, and all of our country. The government then closed borders, stopped travel, and initiated social distancing measures. The situation escalated overtime to stay at home orders, prohibited social gatherings, closed schools, universities, and stores, except for essential shops. Most businesses closed or sent employees to work from home. With these measures, Austria rejected herd immunity, without sufficient testing and available vaccines for the disease.

The Swedish approach

In contrast, Sweden opted for minimal measures to reduce coronavirus spread, based on everyone getting sick, with the assumption that only 1% of infected people die, and survivors have protective immunity. However, a problem with the Swedish approach is a high death rate (217/1 million people) compared to countries with strict measures, like Austria (60/1 million people).

Another problem with everyone getting sick at the same time is that there may be insufficient capacity in hospitals and intensive care units for the severely ill, and then more people will die. We recently saw this happen in New York City. There are also reports of potential chronic health problems, even in younger patients, after surviving severe COVID-19.

A major obstacle with herd immunity was presented last week in the scientific brief issued by the World Health Organization (WHO). They stated that there is no evidence that antibodies against COVID-19 protect people who have had the disease from a second infection. For herd immunity to work, a large percentage of COVID-19 survivors or people vaccinated in the population are then assumed to protect people without immunity. In other words, this means, protection by the immunity of others.

Too many unknowns

There is no basis for this assumption. Without protective antibodies from having had or being vaccinated against the disease, herd immunity cannot guarantee that outbreaks are less likely and that people without immunity to SARS-CoV-2 will be safe.

There are still too many unknowns when it comes to SARS-CoV-2 immunity to consider herd immunity as the basis for reopening society. One is the lack of evidence about whether the antibodies are even protective, if you have them. Another is that even if antibodies are protective, we don’t know if there is lifelong immunity to SARS-CoV-2. To restart life safely, we need protective antibodies, or outbreaks will happen again.

So to be clear: We would love to have herd immunity; it would be wonderful if everyone, or even a solid majority, were immune. So, we are working in that direction – but not all at once and not in a rush for the reasons above. It’s just too dangerous.  

Until we know more about coronavirus immune responses, the slow, step-by-step approach that our Austrian leaders are taking to reopen the country – as outlined in a recent CNN interview with the chancellor – is the one that will best reduce the significant loss of life caused by a premature attempt to apply a principle of herd immunity that is as yet unproven.

(Foto: Dibya Jyoti Ghosh on Unsplash)

Dr. Michelle Epstein
Michelle Epstein is a medical doctor graduated from the University of Alberta in Canada, who has specialised in Internal Medicine at the University of British Columbia and Allergy and Clinical Immunology at Yale University. Since 2004, she has been a Lab Leader at the Medical University of Vienna’s Division of Immunology.

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