Vaccines, Herd Immunity, and COVID-19

Abstract

Vaccines in America have led to the eradication of transmissible infections and the reduction of vaccine preventable diseases among all age groups. Vaccines are important to the safety and welfare of our nation because vaccines produce immunity from infectious diseases. When most of the American population is vaccinated against COVID-19 and other transmittable diseases, herd or community immunity can slow disease transmission, including protection against the disease among persons who have not received the vaccines, and reduce the risk at-large of severe infections and adverse consequences of those diseases.

Vaccines are recognized as one of the greatest public health accomplishments in American history (Malone & Hinman, 2017; Ventola, 2016). Vaccines have led to decreases in morbidity, mortality, prevalence, and incidence of diseases worldwide (Centers for Disease Control and Prevention [CDC], 2016a). Today, the world is facing a deadly viral disease, COVID-19, that has taken the lives of over 1.8 million people world-wide and more than 352,000 Americans (John Hopkins, 2021). Americans are eligible to receive the Emergency Use Authorization (EUA) recently approved vaccines for the SARSCoV-2 virus. The public health of these vaccines is to achieve herd immunity here in America and around the world.

In this discussion of COVID-19, the focus will be upon the Centers for Disease Control and Prevention’s (CDC’s) definition and management of “Community Immunity (Herd Immunity)” in America, to differentiate between vaccination and immunization, and to consider their roles in fostering herd immunity during the COVID-19 pandemic (U.S. Department of Health & Human Services [HHS], 2021; CDC Advisory Committee on Immunization Practices [ACIP], 2021b). The purpose of this paper is to describe the role of the CDC in promoting herd immunity and the vaccination of U.S. citizens. The premise of this paper is based upon the belief that vaccines save lives.

The Role of the CDC in Addressing Herd Immunity

Herd immunity describes how immunizations protect groups of people from vaccine-preventable illnesses by decreasing the incidence and opportunity for the outbreak of diseases (HHS, 2021; Fine et al., 2011). The importance of herd immunity is that it protects persons who have not been immunized for illnesses, such as immunocompromised individuals, infants, pregnant women, and disparaged populations (HHS, 2021; Raman et al., 2021).

The role of the CDC in addressing herd immunity is to control the spread of contagious diseases in America, including communicable diseases like COVID-19, measles, mumps, rubella, varicella, influenza, pneumonia, rotavirus, and others that can be prevented by vaccines (CDC, 2018, 2021a, 2020b; Fine et al., 2011). The CDC is responsible for ensuring vaccine safety, including minimal adverse effects to the community receiving the vaccine, and to avoid creating vaccine hesitancy among population groups (Malone & Hinman, 2017).

To reduce the risk of transmitting infectious diseases, higher rates of community members who have received vaccines against transmittable diseases creates herd immunity (Malone & Hinman, 2017; HHS, 2021). Herd immunity provides protection to the small number of community members who do not receive vaccinations, thus lowering the risk of infection for the community overall (Malone & Hinman, 2017). The CDC recommends that to stop the spread of COVID-19, at least 80% of the U.S. population should be vaccinated against SARS CoV-2 (CDC, 2021b).

The CDC oversees the National Immunization Program’s vaccine safety activities which ensure the public safety of vaccine recipients. The CDC provides Vaccine Information Statements (VIS) to parents and vaccine recipients that outline the purpose of the vaccine, possible side effects or adverse reactions, along with a contact number at the CDC for reporting any such incidents (CDC, 2016b). The CDC provides free vaccinations to uninsured children, those whose insurance does not provide vaccine coverage, and children insured under the Medicaid program. Additionally, the CDC offers grants to health departments that provide immunization programs to children (Malone & Hinman, 2017).

Vaccines

Vaccines do not cause disease; they mimic the viral or bacterial disease, and this activates the body’s immune response. Vaccines are important to the safety and welfare of our nation because vaccines produce immunity from diseases. They are deliverable by several routes of administration such as injection, aerosol, or by mouth (CDC, 2019; HHS, 2021). Vaccination contents may contain killed or weakened organisms that boost the immune system to develop immunity against that organism, or they may contain synthetic viral protein replicas coated with a lipid-nano protein covering (Brown & Bhella, 2016; Food and Drug Administration (FDA), 2020a, b; HHS, 2021). In live attenuated virus vaccines, the original virus has been altered so that virulence is minimized, yet the ability for viral replication and immunogenicity is maintained (Crommelin et al., 2021). Once an individual develops immunity against a virus, the individual is protected against that viral disease, reducing the rate of spread within a community (HHS, 2021).

Viral Vector Vaccines

Antigens are essential for vaccine science because they induce immunity and can provide lifelong protection against diseases. Recombinant viral vector vaccines are used to deliver proteins that are foreign to the human body and induce protective antibodies through an immune response by mimicking a natural infection (Lauer et al., 2017). Examples of viral vectors are adenoviruses (currently used in the single dose COVID-19 vaccine), the measles virus, and poxviruses. These viruses qualify as viral vectors because they provide the following: (1) a proven safety record, (2) stable insertion of coding sequence into the genome, (3) a protective immune response induction, and (4) the potential for large-scale production around the world (Lauer et al., 2017).

Research suggests that viral vectors can be used to protect against a broad range of infectious diseases such as malaria and tuberculosis. The goal in using viral vectors is to allow for a single vaccine agent to protect against several common global pathogens, while simultaneously employing well-established and safe vectors in a cost-effective and unified program (Lauer et al., 2017).

There are also deficient viral vector vaccines that consist of biologically engineered viral vectors that cannot replicate except upon administration and cellular penetration. Currently, there are two non-replicating viral vector vaccines approved by the European Medicines Agency to treat the Ebola virus. The vaccines work by allowing for the expression of the specific encoded antigen (Adenovirus [AdV-26] and Modified Vaccinia Ankara vectors) (Crommelin et al., 2021). Oxford/ Astra Zeneca (ChAdOx1 nCoV-19) and Johnson & Johnson (J&J) (Ad26.COV2.S) received emergency use authorization (EUA) for distribution and administration of two adenoviral vector vaccines that are stored in frozen liquid form at (20°C) (Crommedin et al., 2021). Once an individual develops an immunity against an organism, the individual is protected against that disease, reducing the rate of spread within a community (HHS, 2021).

Vaccination Versus Immunization

The terms vaccination and immunization are often used interchangeably. However, a vaccination requires introducing an antigenic material into the body via injection, aerosol spray or orally, to stimulate an immune response to a specific disease. An immunization is a process used to provide protection against a disease by producing immunity against a foreign antigen without causing the disease. The success of any immunization program is predicated upon the amount of time needed for an individual to develop antibodies or an immune response. An immune response is determined by the disease and the length of time required for a vaccine to establish that it prevents the disease or decreases the severity of the disease in a minimum of 50% of vaccinated people (HHS, 2021; FDA, 2020).

In a study by Matsuoka et al. (2016), researchers investigated various factors related to the spread and prevention of influenza A (H1N1) among children. The study was conducted on residents from Hiroshima Prefecture, Japan, and showed a 53.5% response rate (Matsuoka et al., 2016). The pandemic vaccine effectiveness (VE) ratio of non-vaccinated children to the influenza A vaccinated children’s group was 2.18 (95% confidence interval [2.13–2.23]) (Matsuoka et al., 2016). The study showed that in children ages 7 to 15, there was a higher incidence of transmitting the H1N1 virus from infected to susceptible and greatly contributed to the level of herd immunity to influenza. Matsuoka et al. (2016) concluded that to decrease the level of outbreaks of H1N1, vaccines should be provided to at-risk populations and also include populations (children) who are likely to spread the H1N1 disease.

Vaccine Hesitancy

Despite the research on the effectiveness of herd immunity, vaccines as a matter of public health face several obstacles, such as skeptics, vaccine hesitancy, lack of trust, and those who are unsure of the significance of vaccine prevention (Dreger, 2015). England and England (2016) challenged anti-vaccine proponents who claimed that certain vaccines cause autism despite contradicting scientific evidence. Dreger (2015) shared blog conversations which emphasized that “vaccines don’t just protect the individual being vaccinated; they also help to create herd immunity.”

The argument in favor of vaccines suggests that vaccines are essential to the welfare and wellbeing of our nation. The history of vaccines and the number of lives that have been saved is believed to be partly due to herd immunity (CDC, 2015). One example is the prevention of the measles outbreak (CDC, 2020a). The measles virus is a “highly-contagious airborne disease that causes sneezing, coughing, fever, runny nose, sore throat and red eyes, with the later appearance of a generalized skin rash” (Heuther et al., 2016). A fundamental issues remains: if the consequences of acquiring certain diseases are minor, then should we continue to recommend the related vaccines? For example, targeting human papillomavirus (HPV) in males surfaces a question of policy on whether to vaccinate males in order to protect females who are at a greater risk of injury from HPV (Fine et al., 2011).

Herd Immunity

Research suggests that three out of ten people infected with the measles virus will develop complications of the disease such as pneumonia, diarrhea, or ear infections (CDC, 2020a). There are approximately 20 million people worldwide who are infected with the measles virus annually and approximately 146,000 casualties (CDC, 2020a). In 2000, America declared that the measles virus was eliminated and reported incidences as low as 37 cases. Since that time, the number of reported measles cases has risen to approximately 668, mostly from persons entering the U.S. from foreign countries. It is accepted that herd immunity has played a major role in preventing the rapid spread of measles in America, partly due to the many children and adults who have received the measles vaccine to boost their immune system against the disease (CDC, 2020a).

The idea of herd immunity reached a milestone when Smith in 1970 and Dietz in 1975 (Fine et al., 2011) developed a theorem demonstrating what successful vaccinations would look like. The theorem described how a random distribution of a non-immunized group coupled with a random mixing of the immunized population on average led to reduced transmission of the infection. Examples of Smith and Dietz’s theories can be seen in the appearance of childhood infections such as measles, mumps, rubella, pertussis, chickenpox, and polio increased when large numbers of non-immunized or susceptible persons were found in a certain population. However, the rate of incidence was effectively contained when the numbers of susceptible individuals were maintained at a certain threshold in which the proportion of immune persons protected the others, creating herd immunity (CDC, 2016a; Fine et al., 2011).

There is much to be said about the importance of herd immunity; in the U.S. it has led to a reduction in diseases among cohorts too old or too young to have been vaccinated. Currently two messenger (m) ribonucleic acid (RNA) vaccines have been approved for a two-dose regimen. Pfizer-BioNTech COVID-19 vaccine is given 21 days apart and Moderna COVID-19 vaccine has a 28-day interval (Hinton, 2021, February 25; Hinton, 2021, May 10). Both mRNA vaccines are showing approximately 95% efficacy in preventing COVID-19 disease in adults (U.S. Food and Drug Administration (Hahn, 2021). The goal for the new COVID-19 vaccines produced by Pfizer-BioNTech and Moderna is to create herd immunity by slowing down the disease transmission in the general population for those who may be at risk for severe infections and the difficulties of COVID-19 infection (Hinton, 2021, February 25; Hinton, 2021, May 10).

Importance of Vaccines

On an annual basis, the Advisory Committee on Immunization Practices (ACIP) publishes its recommendations on the use of vaccines in America (CDC, 2021b). The ACIP Adapted from: CDC, 2020b Diseases 20^th Century Morbidity 2019 Reported Cases % Decrease Smallpox 29,005 0 100% Diphtheria 21,053 2 >99% Pertussis 200,752 15,662 92% Tetanus 580 8 99% Polio (Paralytic) 16,316 0 100% Measles 530,217 1,287 >99% Mumps 162,344 3,509 98% Rubella 47,745 6 >99% Haemophilus Influenzae 20,000 (est.) 270 (16 serotype B /254 unknown) 99% COVID-19 12/20/2020 21^st Century 312,636 21^st Century 17,391,270 0 also provides the most current immunization schedules, outlining risks, benefits, and potential adverse effects of vaccines (CDC, 2021b). Because COVID-19 vaccines have an EUA designation, they are listed as experimental vaccines. Even so, the U.S. Food and Drug Administration (FDA) has provided fact sheets which outline important information about the vaccines, including findings of studies, side effects, contraindications, adverse events, and administration requirements (CDC, 2015; Hinton, 2021, February 25; Hinton, 2021, May 10).

Vaccines provide an opportunity for lifetime protection against certain diseases. The incidence and mortality rates of many diseases have declined or become non-existent due to the advances of vaccine therapy (see Table 1) (CDC, 2021c). Historically, several diseases were prevalent in the 20^th century, impacting the lives of many Americans. In 1900, there were 21,064 reported cases of smallpox, with 894 deaths. In 1920, there were 469,924 reported cases of measles with over 7500 deaths and 147,991 reported cases of diphtheria cases with over 13,000 deaths. In 1922, there were 107,473 cases of pertussis with 5099 deaths (CDC, 1999). These morbidity and mortality figures reflect a lack of vaccines; incidence and mortality rates have fallen precipitously since the development and public health policy-driven roll-out of vaccinations in the U.S. over the last century.

Table 1.

21^st and 20^th century morbidity of preventable diseases

Diseases	20th Century Morbidity	2019 Reported Cases	% Decrease
Smallpox	29,005	0	100%
Diphtheria	21,053	2	>99%
Pertussis	200,752	15,662	92%
Tetanus	580	8	99%
Polio (Paralytic)	16,316	0	100%
Measles	530,217	1,287	>99%
Mumps	162,344	3,509	98%
Rubella	47,745	6	>99%
Haemophilus Influenzae	20,000 (est.)	270 (16 serotype B /254 unknown)	99%
COVID-19 12/20/2020	21st Century 312,636	21st Century 17,391,270	0

Adapted from: CDC, 2020b

Since the 1900s, medical discoveries have led to the development of vaccines against 21 other diseases, with 10 vaccines recommended for use in selected populations at high risk due to age, medical condition, risk behaviors, or area of residence. The other 11 are recommended for all children in America (CDC, 1999). Based upon reports from the CDC, there has been a decline in morbidity from nine vaccine-preventable diseases and their complications, with eradication of smallpox and poliomyelitis (caused by wild-type viruses), and a decline in measles and Haemophilus influenzae type b (Hib) among children less than five years of age. The CDC reports a 75% reduction in measles deaths from 2000–2016 (CDC, 1999).

SUMMARY

Vaccines are among the greatest public health achievements of the 20^th and 21^st centuries. Vaccines can prevent disability and death from infectious diseases and can help to control the spread of infections within communities by creating herd immunity, because vaccines protect more than the vaccinated individual; they also protect society. To that end, the CDC holds great responsibility in protecting the nation against communicable diseases. Following the CDC’s recommendations regarding vaccination practices is fundamental to creating herd immunity that effectively protects the community from the incidence and spread of vaccine preventable illnesses, which is particularly important in the era of the COVID-19 pandemic.

Biographies

Linda Washington-Brown, PhD, EJD, MSN, PNP, FNP, ANP-C, FAANP, FAAN is the President and Director of Xspurt Provider Services, a telehealth healthcare service. Since 1999, Dr. Washington-Brown is the retired founding Associate Dean for the RN to BSN Program at Broward College. She is also the Vaccine Program Coordinator of the Miami Rescue Mission Clinic Immunization Program. Dr. Washington-Brown is the immediate past-President of the Miami Chapter, Black Nurses Association (BNA); Lifetime member of the National BNA (NBNA); Chair, NBNA Diversity and Inclusivity Committee; co-Lead NBNA representative for the Health and Human Services (HHS) Vaccine Panel; Co-chair for the newly formed AANP Community-Health Equity/ Diversity and Inclusion Special Interest Group (SIG); and Co-chair of the American Association of Nurse Practitioners Nomination Council. She is a former post-doctoral Fellow from the University of Pennsylvania and an American Nurses Association Minority Fellow alum. Dr. Washington-Brown’s focus area is providing primary care services to diverse and vulnerable populations locally and internationally, creating herd immunity among homeless men and women through her vaccination project that advances nursing practice and science. She has also provided international healthcare services to disparate groups in Jamaica, Haiti, and Ecuador over the past five-years and educational training to nurses and medical students in Guayaquil, Ecuador.

Rose Wimbish- Tompkins, PhD, MSN, RN, is Program Manager of the RN to BSN Program at Broward College.