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Herd Immunity: Marathon or Sprint for COVID-19?

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March 18, 2021

Herd Immunity: Marathon or Sprint for COVID-19?

Jennifer Morency

picture Herd Immunity: Marathon or Sprint for COVID-19?

The world has now reached the one-year mark of the COVID-19 pandemic. It has officially been one year since the coronavirus was dubbed a global pandemic and altered the lives of billions across the world.

Globally, since the start of it all, there have been 120 million cases of coronavirus. In the United States alone, there have been over 29.4 million cases and over 535,000 people have sadly lost their lives to the novel virus.

As countries, regions and sovereignties pooled together immeasurable resources to combat the virus, the unthinkable was accomplished and a vaccine was developed in under a year. Currently, there are three vaccines that have been authorized to be distributed and administered to populations across the United States, notably the Pfizer-BioNTech vaccine, the Moderna vaccine and Johnson & Johnson’s Janssen vaccine.

According to the Centers for Disease Control and Prevention’s (CDC) COVID Data Tracker, nearly 136 million vaccine doses have been delivered across the U.S. and over 109 million have been administered. This results in over 71 million Americans having received at least one dose of a COVID-19 vaccine and 38.3 million having been fully vaccinated against the coronavirus.

The White House also put forth a Fact Sheet on March 11, 2021, announcing that a new strategy has been put in place for COVID-19 vaccinations:

“Today, in the next phase of our vaccination effort, the President will announce that he will direct states, Tribes, and territories to make all adults eligible for the COVID-19 vaccine no later than May 1st. The White House COVID-19 Response Team has concluded that our accelerated vaccination efforts will enable prioritized vaccinations to be far enough along by end of April that all eligibility restrictions for vaccinations can be lifted by May 1st.

Once all Americans are eligible to be vaccinated, the Administration will ensure that every adult is actually able to get the vaccine by increasing the number of places Americans can get vaccinated.”

By increasing the number of places Americans can get vaccinated as well as increasing the number of people providing and supporting vaccines, the United States is on a better and quicker path to immunizing their populations and ultimately reaching herd immunity.

The Importance of Herd Immunity

In order for the United States to attain herd immunity, a certain proportion of the population must be immune to the coronavirus, thus diminishing the likelihood of spreading the virus from person to person.

Of course, in order to achieve herd immunity, the threshold proportion, or percentage of the population who have or had COVID-19 and are thus considered immune, must be greater than the rest of the population. Thankfully, with the vaccine, we can now add to the immune list the number of people who have received at least one dose of either vaccine, increasing the chances of reaching herd immunity.

This leads us to the two paths a population can reach herd immunity – infection and vaccines. Of course, the best way of reaching herd immunity in an ideal situation is through vaccines. They allow people to develop an immunity to the virus without causing illness or putting anyone at serious risk. The more people who become immune to COVID-19, the better everyone is at protecting the rest of the population that is unable to get vaccinated, such as newborns or people with compromised immune systems.

Vaccines are not foolproof however, as some vaccines require revaccinations over time and there is, of course, the human factor of some refusing to be vaccinated due to various beliefs, objections or fears. This can pose a serious threat when many people in a same community choose not to be vaccinated and fall below the herd immunity threshold, potentially sparking a virus outbreak.

Another way of reaching herd immunity is through natural infection. Statistics show that over 29 million Americans have now contracted and recovered from coronavirus since the start of the pandemic. This translates to roughly 8.7 percent of the population having naturally become immune to COVID-19. However, experts are still unsure if whether an individual is truly immune to the virus after contracting it, or if they are still at risk of future infection, especially with the variants currently spreading across the world.

Relying on natural infection alone, experts believe that 200 million Americans (70 percent of the population) would need to recover from the coronavirus to stop the pandemic. The health system’s capabilities in a time of health crisis also comes into play here, as the number of people who become sick at once in a certain area will affect what healthcare professionals can handle and the number of people who potentially recover.

As there is no set rule when it comes to the exact percentage of immunity that a community needs to be to achieve herd immunity, it can be difficult to establish a precise threshold. The general rule seems to revolve around the illness’ contagion level. The higher the level of contagion, the higher the percentage of the population needs to be immune to the disease or virus before herd immunity can be truly reached. When it comes to COVID-19, experts are pushing for anything between 65 percent and 90 percent of the population being immune before preaching herd immunity.

Herd Immunity Threshold for the United States

With the current rate of vaccinations in the United States, coupled with the percentage of the population that has now contracted and recovered from the coronavirus, the herd immunity threshold timeline is looking better and better.

Biden’s vaccination plan, combined with the natural immunity that is slowly being developed across the country, has put the U.S.’ timeline for herd immunity around June or July of 2021. Manufacturing and shipping details for various COVID-19 vaccines shows that the United States should have enough supplies to vaccinate everyone who wishes to be by May or June of this year.

Furthermore, as this is a respiratory virus, scientists are pointing out that the coronavirus is seasonal, in a sense, making immunity in the summer less required than in winter. Dr. Christopher Murray, director of the Institute for Health Metrics and Evaluation, for example, said that based on these facts, he would require a herd immunity threshold of 65 percent in the summer and 85 percent in the winter.

Naturally, we must now take into account the coronavirus variants, which may pose a threat to the herd immunity progress, thus potentially altering the threshold timeline. At this point in time, the goal is to reach a certain number of people who are considered immune to COVID-19 so that the virus can no longer jump and halts the epidemic.

Dr. Christopher Murray, director of the Institute for Health Metrics and Evaluation, would require a herd immunity threshold of 65% in the summer and 85% in the winter, according to his expertise.

Ensuring COVID-19 Transmissions Slow Down

Unfortunately, there is no magic number for the exact number or percentage of the population that is needed to reach herd immunity. On top of this, experts cannot positively say that the COVID-19 vaccines will protect the population to a point where individuals stop spreading the virus.

Communities must play their part in educating their populations and providing adequate access to vaccination sites. Collaborations must be made between local community organizations, political leaders and health authorities. The rest of the population, on their end, must remain vigilant going forward by continuing to wash their hands, social distancing and wearing a mask, whether they are vaccinated against the coronavirus or not.

In order for Americans to get back to a semblance of normalcy, hopefully in 2021, measures and rules must continue to be respected. The more people are vaccinated, and the more restrictions are slowly lifted, the better the chances of seeing how the virus persists and what normal will look like going forward. Seasonality and vaccination coverage will play important roles at this point.

One thing is for certain though, with every day that passes, more and more Americans are getting vaccinated or recovering from natural infection of the coronavirus, inching the United States closer and closer to herd immunity.