Post vaccination decline in pneumonia: 10 years of study shows

Vaishnavi Kardale, Bioinformatics Centre, Savitribai Phule Pune University

According to WHO, pneumonia is responsible for 15% of all deaths of children under the age of 5. It is an acute respiratory infection that affects the lungs. It can be caused by bacteria, fungi, and viruses.

What is pneumonia? 

The lungs have small pockets called alveoli. These pockets facilitate the exchange of oxygen and carbon dioxide. At the time of pneumococcal infection, the alveoli get filled with mucus. The spread of mucous makes it difficult for the exchange to occur in the infected individual. As the amount of carbon dioxide rises in the body, breathing becomes painful. To expel the fluid from the alveoli the infected individual coughs out the mucous. This is how pneumonia spreads primarily. A healthy individual that breathes in this air can contract the disease as well.

How can pneumonia be prevented?

Although most healthy individuals can fight off pneumonia, children who have a compromised immune system are at a higher risk of developing pneumonia. Infants are also at a high risk of infection. Pre-existing illness, infections, malnutrition, and undernourishment increase a child’s risk of contracting pneumonia. Preventing pneumonia is essential to reduce child mortality. Washing hands, maintaining sanitation, and avoiding crowding are essential to containing the spread. However, immunization is the most efficient way to prevent pneumonia.

A Study in The Gambia

A study in the Gambia was carried out to analyze the outcome of vaccination after 10 years. Gambia introduced the pneumococcal conjugate vaccine (PCV) in 2009, this was followed by another PCV13 in 2011. The strategy opted was to give three primary doses without any booster or catch-up immunization. A 10-year population survey was carried out in Basse Health and Demographic Surveillance system residents of age 2months or older.

Patients were screened using standardized criteria by nurses. Invasive pneumonia disease (IPD) was defined as “a compatible illness with isolation of Streptococcus pneumonia from a normally sterile site like CSF, blood, or pleural fluid” by the researchers. Disease incidence between the period of 2008/2010 and 2016/2017 was compared. 22728 patients were identified for investigation, 342 cases of IPD, and 2623 cases of radiological pneumonia were detected. In many middle and high-income countries, a significant reduction in IPD was found. These countries gave either 2 primary shots and a booster shot or 3 primary shots with a booster shot.

Gambia introduced the PCV7 vaccine into its Expanded Program for Immunization (EPI) on August 19, 2009, using three primary doses at age 2, 3, and 4 months without any catch-up immunization. PCV7 was replaced by another vaccine PCV13 in May 2011. This approach is implemented in almost all lower-income countries.

What did the research find?

An 80% reduction was observed among children aged 2-59 months, IPD cases declined from 184 cases per 100,000 people in a year to 38 cases per 100,000 people per year. Incidence of radiological pneumonia also declined by 33%, while pneumonia hospitalizations were reduced by 27%. Further in the 5-14 age group, IPD incidence declined by 69% and radiological pneumonia showed a decline by 27%. This study in discussion showed that the routine introduction of the PCV13 vaccine substantially reduced the incidence of childhood IPD and pneumonia in rural Gambia including the elimination of vaccine-type IPD in infants. 

The findings of this study have important implications for many lower and middle-income countries in Africa and Asia as they follow similar vaccination programs. This study can also help countries that have not yet formulated a PCV program. While countries that have introduced PCV with reasonable coverage in the population can expect a substantial decline in pneumococcal disease and severe pneumonia.

Also read: A special protein in rice to protect it against viral infection

Reference:

1. Mackenzie, G. A., Hill, P. C., Jeffries, D. J., Ndiaye, M., S.M.S., & Hossain, I. …Mackenzie, R. (2021). Impact of the introduction of pneumococcal conjugate vaccination on invasive pneumococcal disease and pneumonia in The Gambia: 10 years of population-based surveillance. The Lancet Infectious Diseases. Published. https://doi.org/10.1016/S1473-3099(20)30880-X

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Author info:

Vaishnavi Kardale is a master’s student at the Bioinformatics Centre, Savitribai Phule University. She is interested in protein folding mechanisms and wants to study them further.

Some of her previous publications are:

1. https://bioxone.in/news/worldnews/the-gene-responsible-for-eye-lens-formation-revealed/
2. https://bioxone.in/news/worldnews/comeback-of-tuberculosis-but-its-drug-resistant-now/
3. https://bioxone.in/news/worldnews/a-drug-to-reduce-covid-infection-by-99/
4. https://bioxone.in/news/worldnews/artificial-intelligence-ai-for-efficient-covid-testing/
5. https://bioxone.in/news/worldnews/deephbv-a-machine-learning-tool-to-aid-in-hepatitis-b-integration-site-detection/