The Use of Vaccines Through a Life Time
As we have discussed, the original goal of EPI was to expand vaccination for children, however, the benefits of vaccines are not restricted to children alone. Vaccination can be beneficial for many different groups within our societies. We will discuss the benefits of vaccination in other age groups and for other indications in this step.
The World Health Organisation defines adolescents as between 10 and 19 years old. There are several reasons why vaccination is important in this group:
- To maintain protection against vaccine preventable infections targeted in the childhood immunisation programmes, such as diphtheria, tetanus and polio
- To protect against specific infections which occur more commonly in this age group. In the UK an increase in the incidence of meningococcal serogroup Y infection in this age group resulted in the addition of a meningococcal vaccine to the adolescent vaccine schedule.
- To ensure timely protection. The WHO recommends that human papilloma virus is given to all children. This vaccine protects against infection with the sexually transmitted human papilloma virus which causes cervical and anal cancers. The vaccine ideally needs to be administered before individuals become sexually active therefore this vaccine is given in adolescence.
Vaccination in pregnancy works in several ways:
- Protects the mother from the vaccine preventable infection. For example, influenza can be more severe in pregnancy which can be life threatening for the mother and child
- Protection of the baby through passive immunity. For example, vaccination of pregnant women with pertussis vaccine provides babies with protection against pertussis in the first few months of life prior to the start of the infant immunisation schedules. The protection is provided by protective antibodies produced by the mother being passed through the placenta to the baby. In countries where pertussis vaccine is used in pregnancy a reduction in infant deaths due to pertussis has been seen.
- Prevents transmission of an infection from mother to child. For example preventing influenza and pertussis in the mother means that transmission from mother to child is limited.
- Prevention of specific infections that are of increased risk around the time of delivery. For example, maternal and neonatal tetanus related to birthing conditions in some parts of the world have successfully been prevented by the use of tetanus vaccine. In the future we may have a vaccine for Group B Streptococcal infection which can be acquired by the new born during delivery and causes serious infection.
With increasing age immune responses to both natural infection and vaccines diminish, this is a process called immunosenescence. This means that older adults are more susceptible to infection and may also have more severe disease due to other the presence of other medical conditions.
One of the challenges of using vaccination successfully in this group is the diminished response to vaccines. The use of adjuvants or novel vaccines are needed to optimise vaccine responses in this population.
Individuals with underlying medical conditions
Individuals with underlying medical conditions may benefit from vaccination for the following reasons:
- Increased susceptibility to certain infections due deficiencies of the immune system, damage to their lungs due to chronic lung disease or treatment due to their condition. For example, patients who undergo renal dialysis have an increased risk of acquiring hepatitis B due to the dialysis process if adequate infection control measures are not in place.
- In some conditions individuals may not be more susceptible to infection but may be affected more severely. For example, in diabetes an infection can result in poorly controlled blood sugars which can make the individual unwell.
Healthcare workers have an increased risk of exposure to certain infections during the course of their work. For example, blood borne viruses such as hepatitis B can be acquired through needle-stick injuries, therefore vaccinating healthcare workers against hepatitis B infection can prevent such acquisition. Healthcare workers may also be responsible for transmission of infections within healthcare settings therefore vaccinating healthcare workers against influenza can prevent such transmission.
Vaccines may be used to protect individuals against infections when they travel to parts of the world where a particular infection may be more prevalent than in their own country and also to prevent international spread of infection. For example yellow fever vaccine may be required for entry to some countries where the infection does not occur but the mosquito vector or non-human primate hosts of yellow fever are presents. Vaccination of travellers against yellow fever limits the chances that yellow fever will be imported and spread in those countries.
The table within the reference section below explains how vaccines may provide benefit at different stages of life and health and the vaccines that are used in some groups in some countries.