Can we count on herd immunity to stop Covid-19?

There has been much discussion in regards to the term “herd immunity” and whether it may be achieved in the present Covid-19 situation. What is herd immunity and might we count on it to stop the spread of the brand new coronavirus? Fine, Eames, and Heymann (2011) provide several definitions of herd immunity, including: a threshold percentage of immune individuals that ought to result in a decrease within the incidence of infection or a pattern of immunity that ought to protect a population from invasion by a brand new infection. In her blog titled “What is Herd Immunity?” Lisa Bonsall, MSN, RN, CRNP, discusses how “herd immunity, or herd immunity, makes it harder for infectious diseases to spread, especially among people for whom vaccination is contraindicated.”

How does a community achieve herd immunity?

Herd immunity is achieved when a population becomes immune on account of prior infection or vaccination (World Health Organization [WHO]2020). Individual natural immunity occurs after direct contact with a pathogen. After contracting a viral or bacterial infection, the body produces antibodies to fight the microorganism, and memory cells are also created that help protect the person from reinfection in the long run. For some diseases, corresponding to measles, immunity lasts a lifetime, while for others, corresponding to influenza, immunity lasts only six months to a yr. People who get well from Covid-19 produce antibodies against the virus, but unfortunately we don’t yet understand how long this protective response will last.

When does a community reach herd immunity?

Herd immunity occurs when the variety of immune individuals reaches a degree where the virus can not find susceptible hosts to contaminate and subsequently can not spread. The herd immunity threshold depends upon the transmissibility of the disease and could be calculated from the reproduction number R0 (“R zero” or “R zero”), which tells us the typical variety of folks that an individual infected with the virus can completely infect a susceptible population (Randolph and Barreiro , 2020). The higher the R0, the more contagious the disease and subsequently more people should be resistant to the virus to stop transmission. R0 will rely on population density, population structure, and make contact with rates amongst different demographic groups (Randolph and Barreiro, 2020). While the R0 will vary by city, state and country, scientists consider the R0 for Covid-19 is within the range of two to 3; in other words, one person can infect two to 3 people (WebMD, 2020). This signifies that within the United States alone, roughly 50-70% of the population (over 200,000,000 Americans) would wish to contract the virus and get well to realize herd immunity. Exposing a significant slice of the population is unrealistic and ethically questionable as COVID-19 has caused serious disease leading to excessive hospitalizations, burden on the health care system and, above all, a major variety of fatalities.

The second and preferred approach to achieve herd immunity is thru vaccination, which provides immunity without causing severe disease or negative effects. When enough persons are vaccinated to achieve the herd immunity threshold, individuals who cannot get vaccinated, corresponding to newborns or individuals with weakened immune systems, are protected (Mayo Clinic, 2020). Vaccines have proven effective in controlling infectious diseases corresponding to smallpox, polio, diphtheria, measles, mumps, rubella, varicella-zoster, and influenza, to call a couple of (Amanna & Slifka, 2018).

The biggest challenge is that we’re still months away from an approved vaccine for the novel coronavirus. No vaccine can be 100% effective in every patient. Efficacy will rely on the strength and duration of immunity acquired after the vaccine (Randolph and Barreiro, 2020). Once developed, approved and manufactured, the following hurdle can be distributing the vaccine to billions of individuals world wide. Other problems include vaccines being administered incorrectly outside advisable schedules (Fine et al., 2011) and post-vaccination immunity may wane over time, requiring a booster dose. Viruses are also known to mutate, requiring vaccines to be reconfigured based on latest virus strains. Finally, some persons are reluctant to get vaccinated for religious reasons, fear of vaccine negative effects, uncertainty about safety and advantages, lack of time or money, or feeling it’s inconvenient.

While natural herd immunity is just not the reply to stopping the spread of COVID-19, even when now we have an approved vaccine by early 2021, we’ll still face many challenges in eradicating the virus. As a society, we should be patient, stay the course and individually take responsibility for mitigating the transmission of this disease. Remember to avoid mass gatherings, practice physical distancing, wear a mask in public places, and whenever you cannot maintain physical distance, wash your hands ceaselessly, avoid touching your eyes, nose and mouth, and stay home for those who are sick. Please remember to follow local public health guidelines.

Amanna, I. J., and Slifka, M. K. (2018). Successful vaccines. , 10.1007/82_2018_102. Previous online publication. https://doi.org/10.1007/82_2018_102

Bonsall, L. (2018). What is herd immunity? Lippincott NursingCenter. https://www.nursingcenter.com/ncblog/january-2018/what-is-herd-immunity

Fine, P., Eames, K., & Heymann, D. L. (2011). ‘Herd immunity’: a rough guide. Clinical Infectious Diseases Society of America. https://doi.org/10.1093/cid/cir007

Mayonnaise clinic. (2020). Herd immunity and COVID-19 (coronavirus): What you might want to know. https://www.mayoclinic.org/diseases-conditions/coronavirus/in-century/herd-immunity-and-coronavirus/art-20486808

Randolph, HE, and Barreiro LB (2020). Herd immunity: understanding Covid-19. 52 para 5. 737-741. https://doi.org/10.1016/j.immuni.2020.04.012

WebMD (2020). Herd immunity. https://www.webmd.com/lung/what-is-herd-immunity#1

World Health Organization (2020). Q&A: Serology and COVID-19: What is herd immunity? https://www.who.int/news-room/qa-detail/qa-serology-and-covid-19