There have been many new terms thrown around over the past eight months, many of which are medical in nature. From flattening the curve to social distancing to contact tracing, our vocabularies have expanded to include public health terminologies that we have never before taken the time to understand, let alone repeat. With winter approaching and cases spiking across the nation, it is time we defined exactly what is meant by another term that is frequently used and often misunderstood. A term that is most closely associated with Sweden’s unique approach to the pandemic. And often reported to be irresponsible and ineffective.
“Herd immunity is a concept used for vaccination in which a population can be protected from a certain virus if a threshold of vaccination is reached,” Dr. Tedros, the Director-General of the World Health Organization said in a press conference recently. “For example, herd immunity against measles requires about 95% of the population to be vaccinated. The remaining 5% will be protected by the fact that measles will not spread among those who are vaccinated. For polio, the threshold is about 80%.”
The difference in that definition of herd immunity, to the commonly held perception, is the inclusion of the word vaccination. Few people realize that herd immunity is achieved in conjunction with a vaccination that protects the majority of the population. “Herd immunity is achieved by protecting people from a virus, not by exposing them to it,” Dr. Tedros reiterated last week. “Never in the history of public health has herd immunity been used as a strategy responding to an outbreak — let alone a pandemic. It’s scientifically and ethically problematic.”
One of the central problems is that we don’t have sufficient information about the virus to confidently test out a herd immunity strategy. “First we don’t know enough about immunity to COVID-19,” Dr Tedros says. “Most people who are infected with the virus that causes COVID-19 develop an immune response within the first few weeks but we don’t know how strong or lasting that immune response is or how it differs for different people. We have some clues but we don’t have the complete picture.”
Additionally, there is not one governing body that can mandate that nation states respond to the novel coronavirus in a specific way. “We must remember that this is an uneven pandemic,” the WHO advises. “Countries have responded differently and countries have been affected differently. Almost 70% of all cases reported globally last week were from ten countries and almost half of all cases were from just three countries.”
While Sweden was not one of those countries, the nation of 10-million people has had more than 100,000 cases and lost almost 6,000 people to COVID-19. While these numbers are lower than other countries with a similar population, it is important to note that comorbidities are low in the Scandinavian nation, and universal healthcare ensures its citizens are generally in better health than in countries such as the United States.
These factors certainly play a role in the health of the population and it is not recommended for all nations to adopt Sweden’s risky herd immunity strategy. Instead, the WHO recommends taking action to stop infections from occurring. “Prevent amplifying events, protect the vulnerable, empower, educate and engage communities and persist with the same tools that we have been advocating since day one; find, isolate, test and care for cases and trace and quarantine their contacts,” Dr Tedros said. He believes the solution to surviving the pandemic lies in technological advancement. “This is what countries are proving works every day,” he said. “Digital technologies are helping to make these tried and tested public health tools even more effective, such as mobile applications to support contact tracing efforts.”
Perhaps the next iteration of our public health learning will be technical, as we embrace digital tools and strategies that are supported by experts to make a positive impact.