What is herd immunity?
Herd immunity occurs when enough of the population is immunized against a disease causing the virus or bacteria to be less able to transmit from person to person. This, in turn, offers indirect protection for those who are not or unable to get vaccinated. For example, measles is a disease in which patients, notably children, may develop a red, itchy rash, sore throat, fever, and runny nose. Consequences of getting measles include severe lung disease, swelling and inflammation of the brain which can lead to deafness or intellectual disability, and death. It is known to be highly contagious and transmits through the air. Without vaccinations, the disease can be transmitted very quickly to others and can impact a large population. A vaccine containing weakened measles virus can be administered to help the body’s immune or defense system recognize the measles virus. Once recognized, the body will remember the virus by creating antibodies which are little proteins that are produced by the body to specifically identify a particular virus. The antibodies that the body creates will help fight off future measles infections, or minimize the chances of developing life-threatening complications. Measles is known to be highly contagious, and it is found that to achieve herd immunity 90% of the population must be vaccinated. This means that 9 out of 10 people must be vaccinated, so that the 1 person that is not vaccinated can remain protected. In other words, reaching 90% vaccination rate in measles is enough to break the cycle and prevent the continued transmission of measles through the air, thereby protecting the 10% that are not vaccinated. What components are necessary in herd immunity? Herd immunity in general can be achieved in a couple of ways. One is through natural infection. If enough of the population was infected and subsequently recovered from the disease, the infected person’s immune system has developed antibodies against future infections. Recall that antibodies are proteins that the body produces to identify specific viruses. That means those infected are generally protected against reinfection, which may be enough to break the cycle of transmission of the virus from person to person. This may prevent those who were uninfected from becoming infected if the threshold for herd immunity is met. Another way is through vaccines. Vaccines come in many forms, but the idea is that vaccine components mimic the real virus, and serve as a warning and a signal for the body’s immune system to produce antibodies that recognize the viral or bacterial agent causing the disease. When the person encounters the virus or bacteria, the body’s immune system can recognize them and fight off the virus or bacteria. This, in turn, prevents them from developing the disease or illness. As of August 2021, the U.S. Food and Drug Administration has granted emergency use authorization to a few COVID-19 vaccines, including Pfizer-BioNTech, Moderna, and Johnson-Johnson vaccines. What are obstacles that prevent reaching herd immunity in COVID-19? Because COVID-19 is new compared to decades of research done on measles, it is difficult to know what the threshold is for reaching herd immunity. It could be anywhere between 50 to 90% of the population vaccinated. However, as with many unprecedented diseases and the development of new technologies and vaccines, there are many obstacles that still stand in the way of reaching vaccination levels necessary for herd immunity. One of the many reasons is vaccine hesitancy. As of July 19, 2021, 23% of Asian Americans in Virginia are yet to be vaccinated, 25% in Maryland, and 44% in Washington DC. Vaccine hesitancy can be due to many reasons, including religion, skepticism about benefits, worries about vaccines being developed too quickly, conspiracy theories, anti-vaxxers, political views, and many more. If a large portion of the population chooses to not get vaccinated for any of these reasons, it decreases the chance of reaching herd immunity. Furthermore, it is difficult to affirm duration and degree of protection that the vaccines provide. Levels of antibodies diminish over time decreasing the level of protection. With the continual mutations of the COVID-19 virus, newer and more infectious variants have emerged creating additional challenges to achieving herd immunity. What can you do to help? Understandably, drastic lifestyle changes and decisions about COVID can be difficult to make because of the unprecedented nature of COVID-19. Because of the many of the current obstacles, there is much work that still needs to be done to reach vaccination levels necessary for herd immunity. We have come a long way since the first lockdown. With the increased surge in Delta Variant, it is important to look towards reliable sources of information such as the CDC guidelines and recommendations. This series of articles around COVID-19 is supported by OCA-APA Advocates Greater Washington DC Chapter internship. Lucy Zhengimmunity herd herd immunity measles virus getting measles
