Upside and Downside of COVID-19 Natural Infection and Herd Immunity: Expert
Mon, April 19, 2021

Upside and Downside of COVID-19 Natural Infection and Herd Immunity: Expert


The vaccine for COVID-19 may take years before it is commercially available. So, another method to gain immunity against the disease may be considered. However, this method can result in major issues if leveraged incorrectly. An expert in vaccine research says that community infection to achieve herd immunity may crash the global healthcare system.

The major advantage and disadvantage of leveraging community infection to induce herd immunity were detailed by the Mayo Clinic, an American not-for-profit medical center. Although the method could work to reduce new cases of COVID-19, its application would significantly impact the healthcare system. If the system had a higher capacity to handle patients, the idea might be properly configured to distribute natural immunity in people.

The Global Situation of COVID-19

According to the World Health Organization (WHO) of the United Nations, a total of 10,357,662 confirmed cases and 508,055 confirmed deaths were reported worldwide, as of July 1, 2020. In the last 24 hours, 163,939 new cases and 4,188 new deaths globally were confirmed from reporting agencies. The Americas remained with the highest confirmed cases at 5,218,590 and confirmed deaths at 249,318. It was followed by Europe with 2,728,059 confirmed cases and 197,874 confirmed deaths. The Western Pacific, where the first epicenter was, overtook Africa with the lowest confirmed cases at 217,146. Africa remained with the lowest confirmed deaths at 6,192.

The data from the WHO is slightly lagging behind the Coronavirus Resource Center of Johns Hopkins University (JHU), a private research university in the US. As of July 2, 2020, at 9:33:50 am, JHU tallied a total of 10,664,433 confirmed cases, and 515,542 confirmed deaths globally. The top five nations with the highest cases were the US at 2,684,416, Brazil at 1,448,753, Russia at 653,479, India at 585,493, and the UK at 314,992. More than 50% or 5,451,472 cases were classified as recoveries. Brazil had the highest recovery cases at 805,174, followed by the US at 729,994, Russia at 422,235, India at 347,979, and Chile at 245,443. The figures highlighted that more than half a million people have recovered from the disease and might exhibit some level of resistance against the virus.

These individuals may donate plasma to save others who are in critical condition. The donor's antibodies may help patients fight back the virus, recover from symptoms, and even develop their own antibodies. But do the numbers suggest herd immunity building in communities?



Community Infection and Herd Immunity

It is no mystery that some people infected by COVID-19 do not experience symptoms. Sometimes, they only feel mild symptoms that fail to progress. Their immune system appears to be working in a balanced manner, which overcame the disease and avoided an overreaction to the pathogen. They may possess some level of resistance to the virus. Whether or not they encounter the same virus, their body is unlikely to develop serious symptoms unless they are suffering from other health conditions.

At the Mayo Clinic, Dr. Gregory Poland of the Vaccine Research Group provided insights into herd immunity and how it can be acquired without a vaccine. The most recognized way to achieve natural immunity is via natural infection. If they recover, they are likely immune to the pathogen of that disease. If not immune, they are more resilient compared to someone who has never been exposed to the disease.

In a community, the number of people who are exposed and recover from a particular infection affects the immunity level of everyone. This is commonly discussed in herd immunity – a form of immunity wherein the population of people with resistance is higher than those without. The usual level of resistance to reach herd immunity is between 70% and 90% of the population in a community, which means if a city has 80% of its dwellers immune to measles, the remaining 20% will likely be protected from the disease.

That is the main advantage of achieving natural herd immunity. But its disadvantage can be devastating to the healthcare system, especially now with COVID-19. If natural herd immunity is selected, community infection will be required. Several people in a community must be infected with the pathogen to develop immunity. The problem is the period between the onset of symptoms and recovery.



For COVID-19, the quarantine period is 14 days to determine if the patient will show signs of infection. Once symptoms appear, hospitalization is a must for those with moderate to severe symptoms. Even with palliative care, patients can take weeks to fully recover from the novel coronavirus. One month of battling COVID-19 is a long time for the healthcare system.

Within that period, a single patient who is fighting the disease to gain immunity may spread the virus to healthcare workers through notable transmission modes, such as respiratory droplets and surface contact. If there are dozens of patients that must be attended, more healthcare workers are at risk of contracting the disease. This can easily lead to an increase in infected healthcare workers and occupancy of critical care capacity of a hospital.

On a larger scale, about 70% of the US or over 200 million people must recover from COVID-19 to promote herd immunity. The latest data from JHU only showed less than 750,000 people in the US have recovered from the disease. Thus, leveraging community infection for herd immunity will demand more people to get sick to reach that 70% at best.

At worst, the US healthcare system collapses, cases of COVID-19 will rise among older people and those with chronic conditions, and millions of additional deaths will occur. No matter how promising herd immunity is in this pandemic, health experts prefer slowing down the transmission instead. Until a functional vaccine is available, everyone should do their part to slow the spread of COVID-19 via social distancing, staying at home as much as possible, proper handwashing, proper coughing etiquette, wearing face masks in public, and disinfecting frequently touched objects and surfaces.

The Spanish Flu pandemic in 1918 caused herd immunity worldwide due to the scale of outbreaks. Those who survived became immune against the H1N1 flu, an influenza A subtype. Their immunity also explained why many older adults survived the 2009-2010 swine flu, another subtype of H1N1. But the immunity has been achieved in exchange for millions of deaths.