In the United States (U.S.) vaccines have greatly reduced or eliminated many infectious diseases that once routinely killed or harmed infants, children and adults. It is no secret that vaccinations have revolutionized global health as well. Arguably the single most life-saving innovation in the history of medicine, vaccines have eradicated smallpox, slashed child mortality rates, and prevented lifelong disabilities.¹ Even though vaccine development and vaccination efforts have progressed significantly, protecting against long-standing illnesses will continue to be important in the centuries ahead. The pharmacy technician can begin conversations about the immunologic concepts behind vaccination, describe different vaccine types, and provide specific information about various recommended vaccines to educate their patient populations.

Historical Perspective

The concept of immunity goes back to at least the 17^th century when the emperor of China documented his practice of infecting his troops with smallpox to confer protection from the disease. This practice, known as variolation, involved taking liquid from a smallpox pustule of an infected patient, cutting the skin of an uninfected person, and then introducing the inoculum. Variolation came into fashion in Europe in 1721, with the endorsement of English aristocrats, but later met with public outcry after 2% to 3% of people died following inoculation.¹ Around the same time in the U.S., a program of variolation against smallpox was beginning with general success. However, many physicians who were fearful that inoculation spread the disease and worried about deaths after inoculation opposed the program.

In 1796, Edward Jenner helped advance vaccine safety by observing that dairy farmers did not catch smallpox. He hypothesized that prior infection with cowpox, an illness spread from cattle, might protect against smallpox. His successful use of cowpox material to create immunity to smallpox quickly made the practice widespread in the U.S. This method underwent medical and technological changes over the next 200 years and eventually resulted in the eradication of smallpox. A century later, Louis Pasteur injected a nine-year-old boy who had been bitten by a rabid dog with a weakened form of the rabies virus and saved his life. The rabies vaccine became the next to make an impact in vaccine science.¹

Vaccines against whooping cough, diphtheria, tetanus, influenza, and mumps were developed throughout the 1900s.¹ The 20^th Century proved to be an active time for laboratory development, paving the way for vaccines that have reduced morbidity and mortality rates from infectious pathogens across the globe.²

Impact on Public Health

Many diseases are now preventable using vaccines routinely administered to children and adults in the U.S. (Table 1) and most vaccine-preventable diseases of childhood are at historically low levels. Vaccination with 7 of the 12 routinely recommended childhood vaccines prevents an estimated 33,000 deaths and 14 million cases of disease in every birth cohort, saves $10 billion in direct costs in each birth cohort, and saves society an additional $33 billion in costs that include disability and lost productivity.³ Table 2 compares pre-vaccine era cases and deaths in the U.S. to cases and deaths reported since 2006. ^lMeasles, rubella, mumps, diphtheria, and polio have all been eliminated in the U.S. since the vaccines have become part of recommended childhood vaccination schedules. (Diseases are considered eliminated if no chain of transmission in a given outbreak is sustained for more than 12 months.)⁴

Direct and Indirect Effects of Vaccination

Immunizations against specific infectious diseases protect individuals against infection and thereby prevent symptomatic illnesses. Specific vaccines directly blunt the severity of clinical illness (e.g., chicken pox vaccine) or reduce complications (e.g., zoster vaccine and postherpetic neuralgia). Some immunizations also reduce transmission of infectious disease from immunized people to others, thereby reducing the impact of infection spread. This indirect impact is known as herd immunity.⁵ The level of immunization in a population that is required to achieve herd immunity varies with the specific vaccine and disease. Herd immunity only works for diseases that are contagious, like measles.⁵ For example, herd immunity would not be achieved with tetanus. The bacteria that cause tetanus lives in the soil, so all unvaccinated people would be susceptible and could easily be infected. As a general rule, the more contagious the disease the more people will need to be vaccinated to prevent the disease.⁵ While herd immunity is a benefit to having high vaccination coverage, vaccination remains the best direct protection from vaccine-preventable diseases.

VACCINE INDUCED IMMUNOLOGICAL MEMORY

The mammalian immune response consists of 2 parts: the innate immune response and the adaptive immune response.^6,7 Innate and adaptive responses operate on a continuum to form the full immune response. Innate immunity occurs immediately while adaptive immunity occurs later since it relies on coordination and action of specific adaptive immune cells. 

Innate Immune System

The innate immune system generates rapid, non-specific inflammatory responses in response to viruses, bacteria, and fungi and is the first defense against invading microorganisms. However, it cannot distinguish between specific strains of bacteria or viruses. This defense mechanism consists of physical barriers such as the skin, gastrointestinal tract, respiratory tract, nasopharynx, cilia, eyelashes, and other body hair. Each of these physical barriers produces additional defense mechanisms such as sweat, gastric acids, bile acids, mucus, saliva, and tears to protect the body from pathogens.⁶

If the anatomical barriers are breached and an infection occurs, inflammation is the next mechanism of defense. The inflammatory response leads to recruitment of neutrophils, macrophages, natural killer (NK) and lymphokine activated killer (LAK) cells, and eosinophils. Neutrophils are recruited to the site of infection where they destroy invading organisms. NK and LAK cells kill viruses and tumor cells while eosinophils kill certain parasites effectively. Macrophages help neutrophils destroy the invader, contribute to tissue repair, and act as antigen-presenting cells to the adaptive immune system. When the innate immune system becomes overwhelmed, macrophages alert the adaptive immune system to begin its defense mechanisms.⁶ 

Adaptive Immune System

A pathogen can establish itself within a tissue and begin to replicate in the host when it overcomes innate immune defenses. In that event, an adaptive immune response targeted to specific invading organisms starts. This process requires days or weeks to develop. The body needs a more sophisticated attack and so turns to B-cells and T-cells for this job. These cells are more specialized, with each B- or T-cell bearing unique receptors that recognize specific antigens. Once the macrophage presents the antigen (invader), if a B- or T-cell has a receptor that recognizes the antigen, it will do its job to address the pathogen. B-cells make antibodies that disable pathogens and eliminate their ability to cause an infection. Unlike B-cells, T-cells do not use antibodies to kill pathogens. Instead, T-cells actively destroy infected cells, and signal other immune cells to participate in the immune response. Cytotoxic T-cells destroy infected cells using digestive enzymes. Helper T-cells activate cytotoxic T-cells and macrophages, and stimulate antibody production by B-cells.⁷

Once the pathogen is eliminated during this primary response, small numbers of antigen-specific B- and T-cells survive long-term, sometimes for the host’s entire life, as memory B- and T-cells. These memory cells confer host protection against reinfection with the same pathogen. During a second response, memory cells use their specific antigen receptors to recognize the invading pathogen. This results in their activation and expansion to kill infected cells directly (using T-cells) or generate antibodies (using B-cells) that will neutralize the pathogen.⁷

Achieving Immunity

Vaccination technology takes advantage of the formation of memory B- and T-cells by the body’s own immune system. As a means of generating immunological memory, health care providers give uninfected individuals a controlled infection or exposed to an antigen that elicits an immune response. When these vaccinated individuals are subsequently infected with these pathogens in their environment, their memory B- and T-cells recognize the invading microbes, mount a response, and prevent the micorobe’s spread and ability to cause disease. This secondary response is more rapid and of a greater magnitude than the primary response to the pathogen. Both B-cells and T-cells provide protection for future encounters with their specific antigen. To achieve this type of long-term memory response, vaccines can achieve immunity through either passive or active methods.

Passive Immunity

Passive immunity involves the transfer of antibodies from an immune individual to a non-immune individual to confer temporary immunity. With passive immunity, protection is immediate since the antibodies are already developed, giving it an advantage over active immunity. There are 2 types of passive immunity: natural and artificial.

An example of passive natural immunity is the transfer of antibodies from mother to fetus during pregnancy and through breast milk consumed by an infant. An example of artificial passive immunization would be purifying antibodies from blood collected from humans who have already been exposed to an illness, then injecting them into another patient to provide immunity to the same illness.³⁸ Clinicians use this method in clinical practice when a person is unable to amount an immune response to a particular invading organism. The major disadvantage to passive immunity is that it lasts for only a few weeks or months whereas active immunity is long-lasting.⁸

Active Immunity

Active immunity results when exposure to a disease leads to development of immunological memory and protection from reinfection through the production of antibodies. Exposure to a disease can occur through infection with the actual disease (resulting in natural immunity), or introduction of a killed or weakened form of the disease through vaccination (vaccine-induced immunity).⁸ Vaccination as compared to natural infection does not cause infectious disease or compromise the individual’s life. Thus, vaccine technologies use active stimulation of the immune system to generate protection against the pathogen in the natural environment.

VACCINE TYPES

Effective vaccines activate both the innate and the adaptive immune systems. There are many different types of vaccines, each with advantages and disadvantages. Each vaccine uses a slightly different approach to prepare the immune system to recognize and fight an invading pathogen. The following section summarizes current methods used in vaccine design and Table 3 lists examples of the different types of currently available vaccines.

Live Attenuated

Live attenuated vaccines use a weakened form of a virus that contains antigens that stimulate an immune response. Such viruses have reduced virulence but retain immunogenic antigens that elicit the development of memory cells after 1 or 2 doses. Attenuated vaccines can be made in several different ways. Some of the most common methods involve passing the disease-causing virus through a series of cell cultures or animal embryos (typically chick embryos). The virus is grown in different embryos in a series and with each passage, the virus becomes better at replicating in animal cells, but loses its ability to replicate in human cells. A virus targeted for use in a vaccine may be grown through— “passaged” through—upwards of hundreds of different embryos or cell cultures. ⁸ Eventually, the attenuated virus will be unable to replicate well (or at all) in human cells and can be used in a vaccine. This produces a version of the virus that the human immune system can still recognize, but this version cannot replicate and cause disease in an immunocompetent human host.

Several drawbacks exist with these vaccines. Because they are live viruses, they generally must be refrigerated to retain their activity. In remote areas of the world where refrigeration is unavailable, obtaining and storing this type of vaccine can be a problem. Attenuated vaccines cannot be used in immunocompromised individuals such as patients with HIV or those taking chemotherapy. In people with compromised immune function, viruses have the potential to replicate and could lead to infection. Live viruses are also not generally given to pregnant women.⁸

Inactivated

Killing pathogens using heat, radiation, or chemicals to inactivate them generates the antigenic materials for inactivated vaccines. The dead pathogens can no longer replicate or mutate to their disease-causing state and thus are safe. ³⁹ These types of vaccines are useful because they can be freeze-dried and transported without refrigeration, an important consideration in reaching developing countries. A drawback with inactivated vaccines is that they induce an immune response that is much weaker than that induced by the natural infection; thus, patients require multiple doses to sustain immunity to the pathogen. These extra doses are referred to as booster shots and may be necessary to continue immunity.⁸

Subunit Vaccines

As with inactivated vaccines, subunit vaccines do not contain live pathogens. Instead, subunit vaccines use a component of the microorganism as a vaccine antigen to mimic exposure to the organism itself. Subunit vaccines typically contain polysaccharides (long chain carbohydrates), surface proteins, or toxins that have been isolated from a pathogen and presented as an antigen on its own. Because these subunits may not be presented in native form (i.e., as in the live pathogen), antibodies generated against these antigens may not bind efficiently to the invading pathogen. Therefore, compared to live attenuated vaccines, subunit vaccines induce less-robust immune responses. Since subunit vaccines have no live replicating pathogen present, they usually are considered safe for immunocompromised individuals. Booster shots will likely be required for ongoing protection against diseases since suboptimal immunity is usually produced.⁸

In some cases when the plain polysaccharide does not produce enough of an immune response, scientists bind the polysaccharide to a carrier protein to produce a greater immunological effect. These are referred to as conjugate subunit vaccines. Recombinant vaccines are created by inserting a gene coding for a vaccine protein into another virus in a culture. When the carrier virus reproduces the vaccine, the protein is also created. The result of this approach is a recombinant vaccine that allows the immune system to recognize the expressed protein and provide future protection against the target virus. Toxoid vaccines use a subunit technology approach. In this case, inactivated or killed toxins are used as the immunogenic material. However, because they are not highly immunogenic, they must be adsorbed to adjuvants (aluminum or calcium salts) to increase their capacity to stimulate the immune response. Vaccines against these toxins are effective because they elicit an immune response that results in production of antibodies that can bind and neutralize the toxin, preventing cell damage in the patient.⁸

DNA/RNA Vaccines

DNA and RNA vaccination are alternatives to traditional vaccines and have mainly been approved in veterinary medicine until recently. Although no DNA vaccines have been approved for human use, some COVID-19 vaccines now use mRNA vaccines. The methodology behind this type of vaccination follows the premise that viruses can only multiply in living cells. But to replicate, the virus has to make more protein. DNA becomes RNA, which becomes messenger RNA (mRNA) that makes proteins. The body registers this protein as an antigen. A DNA or RNA vaccine takes a small part of the virus' own genetic information, just enough to spark an immune response, and relies on the human body’s own cells for production of the target protein (antigen). An injection delivers engineered genetic information to the host, which uptakes the DNA or RNA and transcribes and translates it to produce antigenic proteins. The body identifies these antigens and stimulates both B-cells and T-cells to generate immunity.⁹

This approach offers several potential advantages over traditional approaches. DNA and RNA vaccines can be developed in a laboratory using readily available materials. This means the process can be standardized and scaled up, making vaccine development faster than traditional methods of making vaccines.⁹ Some people are under the misconception that this vaccine alters the host’s genetic code, or changes human DNA and/or RNA. This is not true. Genetic vaccines do not enter the human genome, they merely imitate what happens when our body is infected with a virus. A virus inserts its own DNA or RNA into our cells to enable it to replicate and spread. The vaccine does that as well, but in a controlled manner. The vaccine retains only a portion of the virus, such as a specific strand to encode for a protein the body recognizes as foreign; that vaccine does not contain enough viral material to infect the host. Note that when we contract a viral infection, the virus’s DNA or RNA is inside of our cells, but the virus does not usually leave its DNA behind to become part of the human genome.¹⁰

Nucleic acid vaccines are evolving rapidly. Messenger RNA vaccines are now some of the first COVID-19 vaccines authorized for use in the U.S.¹⁰ It may soon be possible to combine different variants of antigens together, in the same vaccine, that cover circulating mutations and lead to fewer required vaccinations. This would represent a major step forward in vaccine development against rapidly emerging threats and pandemics. Table 3 lists the names of recently approved mRNA vaccines for COVID-19.

Recombinant Viral Vectors

Viral vector vaccines use a modified version of a different virus (the vector) to elicit an immune response in the person being vaccinated. Once the vector enters the host cells, the selected antigens will be presented to elicit the immune response.¹¹ FDA gave a viral vector-based vaccine conditional approval for use to vaccinate against COVID-19. This vaccine is based on a naturally occurring, low-prevalence human adenovirus which causes common cold–like symptoms. The deletion of a specific gene renders the adenovirus unable to replicate within humans, transforming it into a delivery vehicle for the genetic material encoding the spike protein of SARS-CoV-2. In this form, the vaccine cannot cause COVID‑19 since it only carries the code to make the spike protein; since the adenovirus cannot replicate in humans due to its weakened form, the host cannot contact adenovirus. The vector will enter a human cell and then manufacture the spike protein that is only found on the surface of the COVID-19 virus. The cell displays the spike protein on its surface, which triggers the immune system to begin producing B-cell and T-cells to destroy the antigen. This also leads to long-term immunity by producing B and T memory cells.¹²

RECOMMENDED VACCINES

The following section groups vaccines by target type (bacteria or virus) that are recommended for U.S. adults and children.

Vaccines for Bacteria

Tetanus Toxoid Vaccine

Tetanus is a disease characterized by prolonged spasms and tetany (muscular twitching and cramps and [when severe] seizures) caused by the toxin secreted by the bacterium C. tetani. Under favorable anaerobic conditions, such as in devitalized or necrotic tissue, or dirty wounds, the dormant spores may convert to active toxin-producing tetanus bacilli to produce the toxin. This toxin blocks inhibitory neurotransmitters in the central nervous system and causes the muscular rigidity and spasms typical of generalized tetanus. Case-fatality rates approach 100% in the absence of medical intervention and even if intensive care is available.¹⁵

Production of the vaccine involves growth of strains of C. tetani followed by inactivation of the toxin with formaldehyde. Tetanus toxoid is available as a single-antigen vaccine and in combination vaccines to protect against other vaccine-preventable diseases including diphtheria, pertussis, polio, hepatitis B, and illness caused by Haemophilus influenzae type b (Hib). The pentavalent vaccine, which provides protection against diphtheria, tetanus, pertussis, Hib, and hepatitis B (DTP-Hib-HepB), is the most commonly used childhood vaccine worldwide. Since the vaccine does not provide lifelong immunity, booster shots are required. Serological survey data suggest that booster doses in adolescents and adults are critical to maintain high antibody levels, and a booster dose is recommended every 10 years.¹⁵

Diphtheria Toxoid Vaccine

Diphtheria is caused by Corynebacterium diphtheriae and is transmitted from person to person through droplets and close physical contact. Infection can cause respiratory or cutaneous diphtheria (sore throat, fever, cough, a grey or white patch in the throat that can block the airway) and in rare cases can lead to systemic diphtheria. Absorption of diphtheria toxin into the bloodstream results in toxic damage to organs such as the heart, kidneys, and peripheral nerves. Diphtheria vaccines contain toxin inactivated by formaldehyde. Diphtheria toxoid is almost exclusively available in combination with tetanus toxoid (T) as DT, or with tetanus and pertussis antigens (DTP). After the primary series of diphtheria toxoid containing vaccine, immunity in childhood wanes over time. Therefore, booster doses are needed every 10 years to ensure continuing protection.¹⁶

Pertussis Vaccine

Pertussis, or whooping cough, is a respiratory tract disease caused by the gram-negative coccobacillus Bordetella pertussis. It is characterized by prolonged sudden and uncontrolled coughing and sometimes, respiratory failure. Epidemic cycles have occurred every 2 to 5 years, even after the introduction of effective vaccination programs and the achievement of high vaccination coverage.¹⁷ Highly contagious, pertussis is transmitted from infected to susceptible individuals by respiratory droplets. Adolescents and adults are significant sources of transmission of pertussis to unvaccinated young infants. Two types of pertussis vaccines are available: whole-cell vaccines based on killed B. pertussis organisms and acellular vaccines based on 1 or more highly purified individual pertussis antigens. Pertussis vaccines are produced as combinations with other antigens and no stand-alone pertussis vaccines are currently marketed.¹⁸ In the U.S., pertussis vaccines are available as diphtheria, tetanus, and pertussis (DTaP) vaccines or tetanus, diphtheria, and pertussis (Tdap) vaccines. Just as with tetanus and diphtheria, a booster dose is recommended every 10 years.¹⁹

Haemophilus influenzae Type B Vaccine

Haemophilus influenza type b (Hib) is a bacterium that is transmitted through the respiratory tract from infected to susceptible individuals. The bacterium infects its host with colonization of the nasopharynx. Following colonization, the organism can cause invasive disease leading to meningitis, pneumonia, septic arthritis, osteomyelitis, pericarditis, cellulitis and epiglottitis or in less severe cases, sinusitis and otitis media. In most populations, the greatest disease burden is seen in children aged 4–18 months.²⁰ This vaccine is a conjugated polysaccharide vaccine and is a recommended part of childhood immunization schedules. The vaccine is only recommended for children younger than 5 unless there are qualifying medical conditions, since insufficient evidence exists to determine the need for a booster dose. Widespread immunization not only reduces disease in those vaccinated, but also reduces nasal carriage (ongoing asymptomatic presence of the bacteria in the nasal spaces) of the bacterium, resulting in reduced transmission to even those not vaccinated and providing evidence of herd immunity.²⁰

Pneumococcal Vaccine

Diseases caused by Streptococcus pneumoniae include pneumonia, meningitis, and febrile bacteremia. Otitis media, sinusitis, and bronchitis are more common but less serious manifestations of infection. The pneumococcal vaccines are designed to cover the serotypes most closely associated with severe pneumococcal disease. As manufacturers developed these vaccines, they have incorporated increasing numbers of serotypes over time.²¹

Two types of pneumococcal vaccines—polysaccharide and conjugate—are available. Routine administration of pneumococcal conjugate vaccine (PCV13) is recommended for all children younger than 2 years of age. For adults routine administration of pneumococcal polysaccharide vaccine (PPSV23) is recommended for everyone 65 years or older. In addition, the Centers for Disease Control and Prevention (CDC) recommends PCV13 for adults 65 years or older who do not have an immunocompromising condition, cerebrospinal fluid leak, or cochlear implant and have never received a dose of PCV13. Anyone who received any doses of PPSV23 before age 65 should receive 1 final dose of the vaccine at age 65 or older with administration of this last dose at least 5 years after the previous PPSV23 dose.²²

Meningococcal Vaccine

Neisseria meningitidis is a significant cause of invasive bacterial disease in childhood, causing sepsis and meningitis. There are 2 types of meningococcal vaccines available in the U.S.: meningococcal conjugate and serogroup B meningococcal vaccines. Routine administration of meningococcal conjugate vaccine is recommended for adolescence 11 to 12 years of age with a booster dose at 16 years of age and for any child or adult at increased risk for meningococcal disease. The serogroup B meningococcal vaccine is recommended for anyone 10 years of age or older who is at increased risk for meningococcal disease.²³

Vaccines for Viruses

Poliovirus Vaccine

Polio is a communicable disease caused by any of 3 poliovirus serotypes (types 1, 2 or 3).²⁴ In the pre-vaccine era when poliovirus was the leading cause of permanent disability in children, almost all children became infected with polioviruses. Polioviruses are spread by fecal-to-oral and oral-to-oral transmission. Where sanitation is poor, fecal-to-oral transmission predominates, whereas oral-to-oral transmission may be more common where sanitation standards are high. In most settings, mixed patterns of transmission are likely. Most people infected with poliovirus do not have symptoms. However, approximately 25% of those infected develop transient minor symptoms, including fever, headache, malaise, nausea, vomiting, and sore throat. In almost all cases, recovery is complete.²⁴ Paralytic poliomyelitis is a rare outcome and occurs when poliovirus enters the central nervous system. Depending on the extent to which motor neurons are affected, temporary or permanent paralysis may ensue. In rare cases, viral destruction is so severe that respiratory paralysis and death may occur. The ratio of paralytic cases to infections is estimated to be approximately 0.05-0.5 per 100 infections depending on the serotype of the virus.²⁵

Inactivated polio vaccine (IPV) is the only polio vaccine that used in the U.S. since 2000. It is available as an injection and the only formulation is a trivalent form containing the 3 virus serotypes. An oral polio vaccine composed of live attenuated polioviruses containing the 3 vaccine strains is not approved for use in the U.S.²⁴ CDC recommends that all children receive 4 doses of the polio virus as part of the standard vaccination schedule. Thanks to widespread use of polio vaccine, the U.S. eliminated polio in 1979.²⁶

Measles Mumps Rubella (MMR) and Measles Mumps Rubella Varicella Virus Vaccine (MMRV)

Measles, mumps and rubella have the same general prodromal symptoms including fever, headache, sore throat, eye irritation, muscle aches, tiredness, cough, or runny nose. Measles and rubella are both associated with a rash, while mumps is more commonly associated with muscle aches, loss of appetite, and swollen glands.²⁷ Varicella (also called chickenpox) is associated with an itchy rash, in addition to fever, tiredness, loss of appetite, and headache. It can lead to serious complications such as pneumonia, encephalitis, or sepsis.²⁸ l

Both MMR and MMRV are live attenuated vaccines. There are 2 options for protecting children against measles, mumps, rubella, and varicella. These include using the varicella vaccine and the trivalent measles, mumps, and rubella (MMR) vaccine as 2 separate injections or using the quadrivalent measles, mumps, rubella, and varicella (MMRV) vaccine as 1 injection. Unless the parent or caregiver expresses a preference for MMRV vaccine, CDC recommends that MMR vaccine and varicella vaccine should be administered as separate injections for the first dose. Refer to Table 4 for the risks and benefits of MMR compared to MMRV for the first dose. CDC recommends that MMRV vaccine generally is preferred over separate injections of MMR and varicella vaccines as the second dose. On the second dose, MMRV vaccine is less likely to cause fever and post licensure studies do not suggest an increased risk for febrile seizures.²⁹

Hepatitis A and Hepatitis B Virus Vaccines

Hepatitis A virus infection causes acute liver disease after transmission by the fecal-oral route. Hepatitis B virus is transmitted by infected blood or other body fluids, including sexual contact and maternal transfer to fetus or infant. Hepatitis B virus can cause a life-threatening and sometimes chronic liver disease.³⁰ The vaccines can be given either as individual injections or in a combined injection that contains both Hepatitis A and Hepatitis B. Hepatitis A is an inactivated vaccine while Hepatitis B is a recombinant vaccine.⁹ Both are part of the childhood immunization schedule.

Rotavirus Vaccine

Rotavirus is the most common cause of dehydrating diarrhea in infants. Its most common symptoms are severe watery diarrhea, vomiting, fever, and/or abdominal pain. Rotavirus is transmitted through infected stool and can be spread by contact with the stool especially in unsanitary conditions. Two rotavirus vaccines are available in the U.S. given as either a 2-dose or 3-dose series depending on the brand. Both vaccines are available as live oral attenuated vaccines and part of the childhood immunization schedule.³¹

Influenza Virus Vaccine

The number of influenza vaccinations administered annually in the U.S. far exceeds that of any other vaccine, because CDC recommends the influenza vaccine yearly for everyone 6 months of age and older. New vaccine formulations for influenza are needed each year because the virus rapidly mutates, which impairs the immune system’s ability to recognize the virus leading to incomplete immunity. Global surveillance and monitoring organizations determine which viral strains are most likely to match the viruses predicted to circulate during the upcoming season. Based on these observations, recommendations are made for the composition of the influenza vaccine for each season.³²

Various flu vaccine manufacturers license multiple influenza vaccine products in the U.S. The CDC recommends use of any licensed, age-appropriate influenza vaccine, including inactivated influenza vaccine, recombinant influenza vaccine, or live attenuated influenza vaccine. No influenza vaccine is preferred over any other.³³ However, the CDC does recommend that people 65 or older receive the injectable vaccine versus the nasal spray. Results from a clinical trial of more than 30,000 participants indicated that the high-dose influenza vaccine was about 24% more effective than the standard-dose influenza vaccine for adults 65 years of age and older.³⁴ The high-dose vaccine contains a higher dose of antigen than the standard influenza injection and in turn, stimulate higher antibody production following vaccination.

Human Papillomavirus (HPV) Vaccine

Human papillomaviruses cause nearly all cases of cervical and anal cancer and many oropharyngeal cancers. Most are caused by just 2 of the many HPV serotypes: types 16 and 18; types 6 and 11 serotypes are responsible for genital warts.³⁵ There is 1 HPV vaccine distributed in the U.S. that is a 9-valent recombinant vaccine that protects against serotypes 6, 11, 16, 18 and 5 additional cancer-causing serotypes (31, 33, 45, 52, and 58) that together account for 10% to 20% of cervical cancers. ^lThe vaccine is recommended for all adolescents 9 to 26 years of age.³⁶

Herpes Zoster Vaccine

Herpes Zoster (shingles) is characterized by a painful rash that develops on 1 side of the face or body. Before the rash appears, people often have pain, itching, or tingling in the area where it will develop. Shingles is caused by varicella zoster virus, the same virus that causes chickenpox. After a person recovers from chickenpox, the virus remains dormant in the body and can reactivate later, causing shingles. The most common complication of shingles is long-term nerve pain called post-herpetic neuralgia. Recombinant zoster vaccine is recommended to prevent shingles in adults 50 years of age and older.³⁷

CONCLUSION

Clearly, immunizations are vital for improving public health and decreasing health care costs. Providing patient education about vaccinations is a place where a pharmacy technician can make a significant impact. A discussion about how vaccines induce immunological memory, specific types of vaccines, and recommended vaccines will help to spotlight vaccination’s ability to improve and maintain a healthy population. Pharmacy technicians can be the first people in the pharmacy setting to begin these conversations and increase public awareness and knowledge about the effectiveness of vaccinations.

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