The Promise Of Herd Immunity

Herd Immunity Could Happen, But Only If A Significant Portion Of The Population Is Vaccinated

YaleCampus

Kate Stout, Writer

As the United States reaches half a million COVID-19 related deaths it may seem like there is no end in sight.  However, herd immunity may soon offer protection to even those that do not receive a vaccine.  

What is herd immunity?  

Herd immunity, also known as community immunity, is the idea that if a large portion of a population is immune to a disease, the others are less likely to catch it.  Beyond a certain threshold, the ability of a given disease or virus to spread is lowered to a crippling level.  

“A situation in which a sufficient proportion of a population is immune to an infectious disease (through vaccination and/or prior illness) to make its spread from person to person unlikely,” the Centers for Disease Control states.  “Even individuals not vaccinated (such as newborns and those with chronic illnesses) are offered some protection because the disease has little opportunity to spread within the community.”  

Herd immunity can be used for protection by those unable to receive vaccines, either out of choice or because they are immunocompromised.  Relying on herd immunity, however, can be dangerous if too many people begin turning down vaccines.  As COVID-19 vaccines are being rolled-out, some wonder if herd immunity is on the horizon.  

Regarding COVID-19 

Herd immunity will not happen overnight, but as the one year mark for the COVID-19 pandemic nears, many are eager to resume their lives.  The promise of vaccinations for the general public, and eventually children, is more than alluring. 

The CDC reports that doctors are not yet aware of what percentage of the population would need to receive a vaccine to achieve herd immunity, but according to the New York Times, the number is somewhere between 70% and 90% of people being immune.  

One major issue regarding herd immunity that has divided some doctors is whether or not those that have already contracted and recovered from COVID-19 should be counted as immune.  With over 28 million recorded cases in the United States alone, being able to include COVID-19 survivors as already protected from the disease could mean less time to make it to herd immunity.  

Although, catching COVID-19 and recovering from it does not always guarantee immunity. In fact, it is possible to catch it twice, even if this is rare.  Dr. Aneesh Mehta from the Emory Vaccine Center explained his view in an interview with CNN.  

The US has had many, many infections, but they’ve been spread out over time. It’s hard to know exactly how many people have been infected, and it appears that certain people lose their immunity some time after infection,” Mehta said. “The goal should be to protect the population through vaccination. 

Additionally, the threat of new COVID-19 variants may compromise the effectiveness of the existing vaccines and the immunity that some COVID-19 survivors have had.  During his interview, Mehta seemed particularly concerned with the strand originally identified in South Africa.  However, Mehta explains that the risks this variant poses could be mitigated by decreasing case numbers in general, making the variant less likely to spread.    

When Can We Expect It  

One study by CNN estimated that the United States could have herd immunity by mid-September, with around 85% of people protected or as early as July with 70% of people vaccinated.  

The study explained that the 28 million people already vaccinated combined with the rapid pace of Biden’s vaccination plan is likely to cause herd immunity sooner rather than later, even if it is impossible to put an exact time on when herd immunity could occur. 

CNN also conducted an interview with Dr. Christopher J.L. Murray who is the Chair and Professor of Health Metrics Sciences and Director of the Institute for Health Metrics and Evaluation at the University of Washington, which provided some happier news.  Murray expressed that herd immunity may be a more season sensitive virus, meaning that as summer comes nearer herd immunity comes too.    

“Respiratory viruses are very seasonal, so the level of immunity required in the summer is much lower than in winter,” Murray said. “Covid is less dramatically seasonal than other respiratory viruses, but as we’ve learned, it still is. I would give a summer herd immunity threshold of 65% and for winter 85%.” 

Vaccine Hesitancy 

Another factor with the potential to harm when and if herd immunity will happen is mistrust of the vaccine.  People fearful of the speed at which the vaccine was produced and the side effects they often cause has pushed many to turn it down.  But this number is not as low as it once was.  More and more people are becoming comfortable with the idea of being vaccinated.  

The Kaiser Family Foundation is a non-profit organization currently working on tracking the public’s opinion and experiences surrounding the COVID-19 vaccines.  They have found a downward trend in public hesitancy regarding being vaccinated.   

In February, they found that 55% of people polled had already been vaccinated or wanted to as soon as possible, a statistic that has increased from 47% in January and 34% in December.  Similar trends have been seen regarding the portion of people waiting to decide if they will be vaccinated. Yet, more than one in twenty people are still entirely against vaccination, unless they are literally forced into it.  

These figures may shift as time goes on, but they do seem to express that herd immunity is more than just a pipe dream.  With only 7% of people solidly against the vaccine, returning to normal as a result of vaccination seems more and more likely.  

Murray summed up the current situation in his interview, explaining briefly what the United States is looking at in terms of COVID-19 and immunity in the rest of 2021.  His message reminds people that while things may still change, we seem to be on the right track. 

“I really do think it will be a quiet summer. But whether it will come back is an open question, that we won’t know the answer to until maybe December,” Murray said. “Two powerful forces — seasonality and the scale of vaccination — combined are going to bring things down pretty steadily, but we’ll have to wait and see.”