Overview

It is a widely accepted fact that as you age and reach your senior years, you become more susceptible to infections. This increased susceptibility is due to several factors such as weakened immune function, physiological changes within the body, and greater exposure to possible infections.¹ However, it is important to take measures to protect yourself from contracting dangerous infections.

Pneumonia is an infection that poses a serious risk to the elderly, often resulting in hospitalisations and further complications.^2,3 Pneumonia is defined as inflammation of the lungs and is associated with many severe respiratory symptoms. Complications from pneumonia include respiratory failure and sepsis, and patients often see their pre-existing conditions worsen.⁴ Vaccination programmes are instrumental in preventing cases of pneumonia in the elderly and reducing long-term effects. In this article, the various vaccination strategies used to prevent bacterial pneumonia in the elderly will be explored in further detail.

Bacterial Pneumonia

Pneumonia is the inflammation of the lungs, often caused by an infection. Pneumonia can be bacterial or viral;⁵ however, this article will solely focus on bacterial pneumonia. Clinically, patients with bacterial pneumonia experience symptoms such as fever, cough, shortness of breath, and chest pain.⁴ Multiple bacteria can cause pneumonia including Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, and Staphylococcus aureus, among others. When these bacteria invade the lower respiratory tract and multiply, the body’s inflammatory response causes the symptoms of pneumonia.⁴ Each of the bacteria responsible for pneumonia has developed specialised mechanisms to avoid the host’s immune response. 

S. pneumoniae is a common bacterial cause of pneumonia. It has a polysaccharide capsule that helps it infect patients and evade the immune system. This capsule acts like armour made of sugar molecules (polysaccharides) surrounding the bacteria. The capsule aids in colonising the respiratory tract and repels mucus, preventing S. pneumoniae from being trapped and cleared from the airways. Additionally, the capsule inhibits certain host immune responses known as the complement pathways.⁶ This capsule is a key target of pneumococcal vaccines.⁷ Other bacteria that cause pneumonia have different mechanisms, such as adhesion proteins and biofilm formation, which enable them to evade the immune system and persist within the host.⁴

As previously mentioned, when an infection takes hold, the host’s immune response is responsible for the inflammation associated with pneumonia. The immune cells in the lungs detect the infection and amass an immune response by releasing molecules called cytokines, which serve various functions. Cytokines are linked to the fever commonly seen in bacterial pneumonia patients. They promote mucus production, attract more immune cells to the site of infection, and cause inflammation in the lungs, which leads to shortness of breath.⁴

While there are treatment options for those who have contracted pneumonia, there are also vaccination strategies that can help to prevent the infection in the first place. These strategies will be discussed below.

Pneumococcal Vaccines

Pneumococcal vaccines protect the body against infections caused by S. pneumoniae, including pneumonia.⁷ There are two types of pneumococcal vaccines: pneumococcal conjugate vaccines (PCV) and pneumococcal polysaccharide vaccines (PPV). Pneumococcal conjugate vaccines contain components of the polysaccharide capsule that are conjugated to non-toxic proteins, while pneumococcal polysaccharide vaccines contain purified capsule polysaccharides alone.⁷ Once introduced into the body, the immune system forms antibodies against these components, and if an infection occurs, the pre-formed antibodies should help control it. In the UK, a few different vaccination types are available, including PPV23 and PCV13. 

S. pneumoniae has many variants (serotypes) that can cause infection.⁷ Components of the polysaccharide capsules from these different serotypes are included in the pneumococcal vaccines. For example, PPV23 contains capsule components from 23 different serotypes of S. pneumoniae, while PCV13 contains components from 13 serotypes.⁷

In the UK, the PCV13 pneumococcal vaccine is administered at 12 weeks of age, with a booster at 1 year, providing protection against 13 serotypes of S. pneumoniae. Then when you reach 65, or if you are at risk of serious illness, you will receive the PPV23 vaccine, which protects against 23 serotypes of S. pneumoniae.⁸ 

Haemophilus Influenzae Type B (Hib) Vaccine

Haemophilus influenzae type b (Hib) is another bacterium that causes pneumonia, as well as other serious infections, including meningitis and sepsis.⁹ In the UK, people are vaccinated either with a combined vaccine that protects against both meningitis C and Haemophilus influenzae type b or as part of the 6-in-1 vaccine.⁹ This vaccine is given at 1 year of age and is not generally readministered to the elderly later in life. 

Influenza Vaccines

Influenza (flu) is a viral infection that predisposes individuals to secondary bacterial infections such as pneumonia.¹⁰ The damage caused by influenza makes the respiratory tract more susceptible to infection by pneumonia-causing bacteria. Viral infections like influenza can alter the cells lining  the respiratory tract, allowing bacteria such as S. pneumoniae to adhere more easily and cause infections.¹¹ Therefore, preventing influenza in the elderly reduces the risk of pneumonia as a secondary infection.

Seasonal influenza vaccines are recommended for the elderly and those with long-term health conditions.¹² The influenza vaccine is updated each year to vaccinate against the most common strains that pose a risk. The World Health Organisation has 147 laboratories in 110 countries monitoring outbreaks, and using this data they decide which flu strains should be targeted by that year’s vaccine.¹³ By vaccinating the elderly against influenza, the risk of developing pneumonia also decreases.¹²

COVID-19 Vaccinations

COVID-19 is another viral infection that poses a risk of secondary bacterial pneumonia infections.¹⁴ The COVID-19 vaccine is currently offered to individuals aged 65 and over or those with long-term health conditions.¹⁵ The COVID-19 vaccine allows the body to recognise the spike protein on the virus and develop immunity against it. At the time of writing, COVID-19 is still a relatively new disease with limited research; however, as with most respiratory viruses, the damage caused by these infections leaves patients susceptible to other infections, including bacterial pneumonia. Therefore, vaccinating against COVID-19 may help reduce the risk of developing bacterial pneumonia.

Summary

In conclusion, bacterial pneumonia is a dangerous infection that poses a significant risk to individuals over the age of 65. Vaccination is an important strategy to help prevent this infection. While there are vaccines against the direct causative agents of pneumonia, such as  S. pneumoniae and H. influenzae, there are also vaccines to prevent other infections that may increase the risk of bacterial pneumonia.

Widescale vaccination of the elderly and those at risk is crucial for both individual and public health. Vaccination can help reduce hospital admissions and the severity of infections. It is important to get vaccinated during the winter months to protect yourself and support public health services.