Vaccine-Preventable Diseases

Edited by Michelle Asselin

Have you ever wondered which vaccines pharmacists are able to inject? Pharmacists who have successfully completed their injection training have the knowledge, skills, and judgment to safely administer vaccines in pharmacies.* This skill has been especially important during the COVID-19 pandemic, as well as during flu shot season. In addition to the COVID and flu vaccines, pharmacists, pharmacy students, registered pharmacy technicians, and interns can also administer vaccines against 13 other preventable diseases.*

Continue reading if you are interested in refreshing your memory or learning more about these 13 vaccines that pharmacists continue to provide to the community.*

1. Bacille Calmette-Guérin (BCG)

Tuberculosis (TB) is an infectious disease caused by the bacteria Mycobacterium tuberculosis. It is transmitted by airborne droplets that mainly affect the lungs. Approximately 33% of the world is infected with TB, while the incidence in Canada is very low. In Canada, TB occurs more commonly among Indigenous and foreign-born individuals. Some of the risk factors for the progression to active TB include immunodeficiencies, diabetes, malnutrition, and smoking. The BCG vaccine has shown to be 51% effective in preventing TB and up to 78% effective in protecting the spread of TB to other areas of the body in newborns. This live vaccine is given as a single injection into the outer layer of the skin and usually leads to redness and swelling in the area, followed by a scar. The BCG vaccine is not recommended for routine use in Canada but is considered for infants in high-risk communities, when there is a high chance of ongoing exposure to TB, and for long-term travellers going to countries where the prevalence of TB is high. The BCG vaccine will not prevent the development of TB in individuals who are already infected.

2. Haemophilus influenzae type B (Hib)

Haemophilus influenzae is a bacterial infection than can cause infections like sepsis (blood infection), meningitis (brain infection), and pneumonia (lung infection). Type B causes 95% of all invasive H. influenzae infections and is therefore targeted through immunization. Hib is spread through coughing, sneezing, or touching contaminated surfaces. Hib occurs worldwide, however infection rates are low in countries with vaccination programs in place. Children under the age of 5 are at the greatest risk of contracting Hib. As a result, vaccination consists of a 3-dose primary series at 2, 4, and 6 months of age with a booster at 12 to 23 months. Following the booster, the vaccine series is 95% to 100% effective against invasive infections. The DTaP-IPV-Hib combination vaccine is commonly used as it provides protection against not only Hib, but also diphtheria, tetanus, pertussis, and polio.

3. Hepatitis A

Hepatitis A occurs worldwide and is one of the most common vaccine preventable diseases. The leading cause of Hepatitis A infection in Canada is international travel. Hepatitis A is a viral infection of the liver and is spread through the faecal-oral route, usually through contaminated food or water. Roughly 25% of adults will become hospitalized, but the mortality rate remains low at 0.5%. Those over 60 years of age, who have pre-existing liver disease or are immunocompromised are at an increased risk for severe illness. The Hepatitis A vaccine (ex. Avaxim, Havrix) is an inactivated virus vaccine administered intramuscularly (into the muscle) as two doses, 6 months apart. The vaccine is nearly 100% effective and is associated with mild fever, soreness at the injection site, and headache. The vaccine is indicated for those 6 months of age or older. To prevent Hepatitis A infection, practicing proper hygiene and avoiding infected water sources, in addition to vaccination, are strongly encouraged.

4. Hepatitis B

Hepatitis B is a DNA virus that is transmitted through contact with infected body fluids such as blood or saliva. Up to 50% of adults and 90% of children will be asymptomatic whereas others could present with fever, stomach pain, loss of appetite, fatigue, vomiting, and jaundice (yellowing of skin and eyes). The initial infection can last up to 3 months and is associated with a fatality rate of 1% to 2%. Most individuals with a Hepatitis B infection recover after 1 to 2 months and they will have antibodies that will provide immunity against future infection. Infected infants, young children, and immunocompromised individuals have the highest risk of progressing to chronic Hepatitis B. Chronic carriers are usually asymptomatic but are more likely to experience complications such as chronic hepatitis, cirrhosis, and liver cancers. The recombinant Hepatitis B vaccine (ex. ENGERIX-B) is given intramuscularly and protects against hepatitis B infection. The vaccine is 95% to 100% effective in preventing chronic infection for at least 30 years after immunization. Vaccine reactions are usually mild and include irritability, headache, fatigue, and pain at the injection site. Routine Hepatitis B immunization is recommended for all children and high-risk groups. In addition, a combination vaccine providing protection against both Hepatitis A and B (TWINRIX) is also available.

5. Varicella

The varicella vaccine protects against chickenpox which is caused by the varicella zoster virus. Chickenpox is spread through the air and through direct skin contact. If infected, mild symptoms usually resolve on their own, but complications such as infection, bleeding disorders, encephalitis, and pneumonia (infection in the lungs) may develop. Most of the severe infections occur in children under the age of 12 who are unvaccinated or immunocompromised. The risk of severe infection increases with age and adults, particularly pregnant women, are greatly affected. The varicella virus vaccine is given as a 2-dose subcutaneous injection (into the fat layer just beneath the skin) to healthy children at 15 months and again at 4 to 6 years of age. It is available as a univalent vaccine (Var) or a combined multivalent measles-mumps-rubella-varicella (MMRV) vaccine. The efficacy of immunization is 98% in children after the second dose. Ultimately, those who are vaccinated and who experience chickenpox will have milder disease than those who are unvaccinated.

6. Herpes Zoster (Shingles)

Herpes zoster results due to the reactivation of varicella zoster virus (chickenpox). Roughly 30% of Canadians will develop shingles with the incidence increasing drastically after the age of 50. Reactivation occurs more often with older age and in immunocompromised individuals. Some people will experience postherpetic neuralgia which is a persistent and debilitating pain around the rash. The herpes zoster vaccine is available as either a live attenuated vaccine (Zostavax) given subcutaneously in a 1-dose schedule, or a recombinant subunit vaccine (Shingrix) given intramuscularly in a two-dose schedule with the doses given 2 to 6 months apart. Either vaccine can be used in individuals over the age of 50, although Shingrix is preferred due to its ability to provoke a better immune response and provide longer protection. Individuals who previously received Zostavax are still encouraged to receive Shingrix for added protection. Since there are few effective treatments for herpes zoster or postherpetic neuralgia, the herpes zoster vaccine should be administered to most individuals as it is safe and effective in reducing complications from infection.

7. Human Papillomavirus (HPV)

HPV is the most common sexually transmitted infection and is spread through direct skin contact with an infected individual. Those who are at greatest risk of infection include individuals who have multiple sexual partners, who had a previous sexually transmitted infection, or are immunocompromised. Most people will be asymptomatic and will pass on the virus unintentionally. Although the incidence of HPV infection is high, most healthy individuals clear their infections after a few years without treatment. Others may develop complications such as genital warts, cervical, vaginal, penile, anal, head or neck cancers. There are many types of HPV, with types 16 and 18 causing 70% of all cervical cancers and types 6 and 11 causing 90% of genital warts. In Canada, there are three HPV vaccines available: bivalent (types 16 and 18 - CERVARIX), quadrivalent (6, 11, 16, 18 - GARDISIL), and nine-valent (6, 11, 16, 18, 31, 33, 45, 52, 58 – GARDISIL9). The bivalent vaccine has shown almost 100% efficiacy against cervical disease. Protection against genital lesions is over 95% and the efficacy against serious disease is over 96%. The HPV vaccine should ideally be provided before the onset of sexual activity as it has no effect on existing infection. A two-dose schedule is recommended for both women and men, starting as young as 9 and up to 26 years of age.

8. Japanese Encephalitis

Japanese encephalitis (JE) is an RNA virus that is transmitted through the bite of an infected mosquito. Mosquitos obtain the virus from infected hosts like pigs and birds. JE is found in Asia and parts of the western Pacific. Overall, the risk of JE is low in travellers, especially those who are travelling to urban areas for short periods of time. However, the risk might be higher depending on the place of visit (ex. rural), season (ex. summer, fall), and type of travel (ex. visiting agricultural areas, camping, hiking). Most people that become infected with JE will be asymptomatic. Approximately 1% of individuals who become infected will develop symptoms and are more likely to experience encephalitis (brain swelling). Up to 30% of those who develop encephalitis will die and up to 50% of survivors will have neurological or psychiatric problems. As a result, the JE vaccine is recommended for travellers with a high exposure risk. In addition to taking the necessary precautions against insect bites, travelers to JE-endemic regions may consider vaccination. IXIARO is an inactivated JE vaccine currently available in Canada and is given as 2 doses, 28 days apart. This vaccine is now indicated for anyone over the age of 2 months and is expected to provide over 95% protection against Japanese encephalitis.

9. Meningococcal Disease

Meningococcal disease is caused by the bacteria Neisseria meningitidis and is the leading cause of meningitis in Canada. Even though infection rates are low, the highest incidence is seen among infants. Meningococcal disease is spread through respiratory droplets, with serogroups A, B, C, Y, and W-135 being associated with severe infection. Individuals at risk of infection include those with sickle cell disease, certain genetic risk factors, respiratory tract infections, recent influenza infection, living in crowded housing, HIV positive individuals, and those travelling to areas with high rates of transmission (ex. sub-Saharan Africa). Up to 20% of survivors may develop complications such as limb amputations, hearing loss, nervous system disorders, developmental disabilities, and seizure disorders. The mortality rate is estimated to be 10%. It’s important to note that meningococcal vaccines are initially highly effective, but effectiveness does decrease over time.

10. Pneumococcal Disease

Pneumococcal disease is a major cause or morbidity and mortality, and is caused by the bacteria Streptococcus pneumoniae. The disease is spread through the air by coughing, sneezing, or sharing items. It primarily affects individuals under the age of 5 or over the age of 65. Pneumococcal disease can lead to localized infections such as ear, sinus, or lung infections. Some people may go on to acquire rare but serious infections like bacteremia (blood infection) and meningitis (infection of the covering around the brain and spinal cord). The mortality rate of pneumococcal pneumonia is 5% to 7% and is even higher in older adults. Children who are under 2, have cochlear implants, attend daycare, have a chronic illness, or are immunocompromised are at an increased risk for pneumococcal disease. Older adults who have a chronic illness such as heart disease, diabetes, and COPD are also at an increased risk for pneumococcal disease. For children, the Pneu-C-13 intramuscular vaccine (Prevnar-13) is recommended for routine vaccination starting at 2 months of age using a 3 or 4 dose schedule. In this population, vaccine efficacy against severe disease if 86% to 97%. For adults over the age of 65, one dose of the Pneu-P-23 subcutaneous vaccine (Pneumovax-23) is available. In the elderly and high-risk individuals, vaccine efficacy is found to be 50% to 80%.

11. Rabies

In Canada, rabies is very rare but is almost 100% fatal if the infection is not prevented and symptoms develop. Rabies occurs worldwide, with most deaths occurring in Asia and Africa. Rabies is an RNA viral infection transmitted through the bite of an infected animal. After becoming infected, the virus will travel to the central nervous system to cause encephalitis[MA2] . Initial symptoms can develop weeks to months after exposure, starting out mild and then quickly progressing to cause more serious implications such as paralysis, seizure, coma, and death. Prevention is the key to rabies management. Travellers should be aware of the risks of rabies and should avoid contact with unfamiliar animals, especially high-risk species like bats and dogs. People at high risk of close contact with rabid animals would benefit from immunization. The duration of travel, travel activities, occurrence of animal rabies in the area, and availability of post-rabies therapies should all be considered when deciding on whether to get the rabies vaccine. In Canada, there are two inactivated vaccines available: IMOVAX and RabAvert. Both are given as a 3-dose schedule at 0, 7, and 21 to 28 days. If immunized before encountering rabies, the vaccine provides antibodies 100% of the time.

12. Typhoid

Typhoid is a bacterial infection caused by Salmonella typhi and is transmitted through ingestion of fecally-contaminated food or water. Travellers are at low risk of infection if they follow safe food and water consumption practices while travelling to typhoid endemic areas. Up to 5% of survivors will become chronic carriers of the bacteria and will risk spreading it to others. In low-income countries, the fatality rate for untreated infections is 10% whereas in high income countries, the fatality rate is less than 1% in treated individuals. India, Pakistan, and Bangladesh have the highest reported risk of infection. As a result, most travellers visiting South Asia should be offered the typhoid vaccine. In Canada, there are several vaccines available for the prevention of typhoid fever and all of them prevent 50% of infections. The intramuscular vaccines (ex. Typh-I) are given as a single dose to individuals at least 2 years of age and they provide protection for three years. Travellers should be vaccinated at least 2 weeks prior to leaving for their trip. The one live attenuated vaccine (Typh-O) is administered as an oral capsule and should be taken every two days for a total of four doses which will provide protection for 7 years. The oral vaccine should not be used in pregnant women, immunocompromised people, individuals with gastrointestinal disorders, or children under the age of 5.

13. Yellow Fever