Common Cold is not Common: Know Why Pneumococcal Vaccines are Important for Adults - Dr Subhashree Samantaray

When people hear the word "common cold" or "flu", they usually dismiss it as a harmless, everyday illness — something that's uncomfortable, but not necessarily fatal.

Though mild, common cold is extremely common, with adults typically experiencing 2 to 3 episodes in a year and even more frequent episodes in children. However, every respiratory infection is not a simple cold.

Few respiratory infections may start with flu-like symptoms, may later on lead to complications like pneumonia, may even worsen the underlying lung conditions like chronic obstructive lung diseases or asthma.

Common cold is mostly viral, causative agents being rhinovirus, seasonal coronavirus, parainfluenza, and human metapneumovirus. Mostly they are self-limiting and can present with runny nose, cough, mild fever, sometimes sore throat.

Sometimes the symptoms may progress over a week to pneumonia presenting with high grade fever, cough with expectoration and difficulty in breathing. The most common cause of such severe illness is the bacteria, Streptococcus pneumoniae.

Such secondary bacterial infections following a viral episode are common, particularly in individuals with chronic conditions like diabetes, chronic heart, lung, liver or kidney diseases, or those on chronic immunosuppressive treatment for some underlying condition.

The pneumococcal vaccine does not directly prevent common colds, which are typically caused by viruses. However, following vaccination, the body can develop antibodies which enable the immune system to fight off the bacteria and prevent the complications like pneumonia, sepsis and meningitis, particularly in individuals with weakened immune systems or chronic illnesses.

Given the synergistic interactions between viral and bacterial pathogens and the hypothesis that the effectiveness of pneumococcal vaccines against all-cause pneumonia might be linked to reduction of viral-associated pneumonia episodes after vaccination.

There are two types of pneumococcal vaccines, the conjugate vaccine and the polysaccharide vaccine. The pneumococcal conjugate vaccine is considered more antigenic, and the polysaccharide vaccine is often used to boost the effect of the conjugate vaccine and create immune memory.

Combined use of both the above vaccines in a phase wise manner has shown 75% efficacy in preventing vaccine-type invasive pneumococcal diseases.

Though not able to cover all the pathogenic serotypes of Streptococcus pneumoniae, the vaccines have shown to provide cross protection against the non-vaccine serotypes as well.

In addition, a randomized controlled trial even showed that the conjugate vaccine has some effect against few viral strains also including human seasonal coronavirus, parainfluenza, and human metapneumovirus. However, no cross protection was observed against adenovirus or rhinovirus in children or adults.

Considering the complications of pneumococcal infection, Government has incorporated pneumococcal vaccination to national immunization schedule for paediatric age group in 2017.

Though we don’t have such a schedule for adult age group, there are multiple bodies like diabetic association of India, Association of Physicians in India, who have recommended the vaccine in all individuals above 50 years and those aged less than 50 years living with comorbidities.

Through vaccination, we can prevent the morbidity and mortality due to pneumonia and reduce the spread of the bacteria in the community.

While the common cold is considered as a mild inconvenience, it’s crucial to recognize the symptoms that can precede serious bacterial infections like pneumococcal pneumoniae.

Pneumococcal disease is a significant threat to adults, especially among the vulnerable ones with comorbidities and chronic illness.

Fortunately, pneumococcal vaccines provide a safe and effective way to prevent these potentially life-threatening infections. Being proactive about adult vaccinations is an important part of maintaining overall health, especially in the elderly or those with chronic health challenges.