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Disease Burden

Pneumococcus disease is a major cause of mortality and morbidity in the world. In 2005, there was an estimated 1.6 million deaths due to pneumococcus disease. Within this estimate, between 0.7 and 1 million were children <5 years old. Most of the deaths occur in poor countries where the annual incidence of invasive pneumococcal disease ranges from 10 to 199 cases per 1000 000 population (1).

In Latin America and the Caribbean, pneumococcal disease causes an estimated 12,000 to 28,000 deaths annually. Every year, pneumococcal cases are also associated with 182,000 hospitalizations (16 per 1,000 children) and 1,412,000 outpatient visits (121 per 1,000 children) (2).

A study released at the 2006 Second Regional Pneumococcal Symposium (3) indicated that pneumococcal disease kills 18,000 children every year in Latin America alone, approximately two children an hour. It is responsible for four major types of illness: ear infections, pneumonia, sepsis and meningitis, three of which can be deadly.

What is Pneumococcus:

Pneumococcus or streptococcus pneumoniae  is a Gram-positive encapsulated diplococcus. The polysaccharide capsule is an essential virulence factor. On the basis of differences in the composition of this capsule, 91 distinct pneumococcal serotypes have been identified. The spectrum of prevalent capsular types varies with age, time and geographical region, although common disease-causing serotypes are consistently identified throughout the world. Approximately 20 serotypes are respomsible for over 70% of invasive pneumococcal disease in all age groups.

Who is at risk:

Pneumococcal carriage occurs in all age groups. The rates of invasive pneumococcal disease are highest in children aged less than 2 years, but disease continues to occur at all ages, with rates among the elderly approaching those seen in young children. In industrialized countries, the highest mortality rate from invasive pneumococcal disease is found among the elderly, who may account for 80% or more of the pneumococcal deaths in these nations (5).

Children under the age of five are at increased risk of contracting IPD as well. Immature immune systems cause young children to be particularly vulnerable to encapsulated pathogens. As such, approximately 80% of all cases of childhood IPD are seen in children under the age of two. Children enrolled in daycare programs and those between two and 11 months of age who are not being breastfed are additionally susceptible to otitis media and invasive pneumococcal disease (IPD) infection. Exposure to cigarette smoke also raises the risk of developing IPD for this population (3).

Each year, children under five years old in Latin America and the Caribbean suffer from an estimated (4):

-1.3 million cases of acute middle ear infections that can lead to deafness

-327,000 cases of pneumonia

-1,229 cases of sepsis (blood infection)

-4,000 cases of meningitis (inflammation of the brain)

Transmission:

Pneumococci are transmitted directly from person to person through close contact via respiratory droplets or by contact with nasopharyngeal secretions of the infected person

Distribution and Seasonality:

Pneumococcus is present in all climates and seasons. In countries with mild climates, there is a slight increase in incidence of pneumococcal pneumonia in the winter and spring months.

Immunity

Newborns have antibodies against the pneumococcal agent that are passively transmitted by their mothers. Within a few months, the antibodies disappear, coinciding with the increase of invasive disease. After repeated exposure to most circulating pneumococcal serotypes, children typically develop a specific immune response against pneumococcal disease after 18 months. 
(3).

Prevention and control

Two conjugate pneumococcal vaccines are currently on the market: the heptavalent and the decavalent. The heptavalent vaccine is recommended by WHO, and the decavalent vaccine is in the prequalification process. The United States (2001), Canada (2002), Bermuda (2008), Mexico (2008), Uruguay (2008), Costa Rica (2009), and Peru (2009) have introduced this vaccine in their vaccination schedule for children aged <1 year.  A 13-valent vaccine was recently licensed in some countries.

 

  1. WHO. 23-valent pneumococcal polysaccharide vaccine: WHO position paper. Weekly Epidemiological Record. 2008; 83, 373–384. Available at: http://www.who.int/wer/2008/wer8342.pdf
  2. WHO. Pneumococcal vaccines: WHO Recommendation. Weekly Epidemiological Record. 2003; 78, 97–120. Available at: http://www.who.int/wer/2003/en/wer7814.pdf
  3. Sinhá A, Constenla D, Valencia JE, O’Loughlin R, Gómez E, de la Hoz F, Valenzuela MT, de Quadros CA. Cost-effectiveness of pneumococcal conjugate vaccination in Latin America and the Caribbean: a regional analysis. Pan American Journal of Public Health. 2008; 24(5): 304-13.
  4. PAHO. “Pneumococcal Disease in Latin America Kills Two Children Every Hour, Causes 1.6 Million Cases of Childhood Disease Every Year, New Study Finds.” Available at: http://www.paho.org/English/DD/PIN/pr061213.htm
  5. Constenla D, Gomez E, de la Hoz FP, O'Loughlin R, Sinha A, Valencia JE, Valenzuela MT. The Burden of Pneumococcal Disease and Cost-Effectiveness of a Pneumococcal Vaccine in Latin America and the Caribbean. Sabin Vaccine Institute 2007; 1:129. Available at: http://www.sabin.org/files/attachment/sabinreportfinal2.pdf
  6. PneumoADIP. Diseases and Vaccines, website. Accessed 24 June 2009. Available at: http://www.preventpneumo.org/
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