Introduction:
Streptococcus pneumoniae (a bacterium) is a global microbe that causes many clinical diseases in children and adults. It causes invasive and noninvasive pneumococcal diseases. Noninvasive pneumococcal disease includes ear inflammation, sinus infections, and community-acquired pneumonia. Invasive pneumococcal disease implies pneumococcal invasion into a sterile (non-infected) site. It further leads to complications such as septicemia, empyema (pus formation in the lung cavity), meningitis (brain infections), endocarditis (heart infection), and osteomyelitis (bone inflammation and infection). Pneumococcal vaccines prevent most of the diseases caused by the bacterium.
What Is the Need for Pneumococcal Vaccines in Children and Adults?
Various reasons for the need for pneumococcal vaccines include:
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The invasive pneumococcal disease is less common than the noninvasive disease. However, it carries a significant mortality (death) risk, that is, up to ten percent for meningitis and 15 percent for septicemia. Furthermore, the survivors suffer from significant disease sequelae.
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With the extensive use of antibiotics and frequent lack of diagnostic data, the burden of invasive pneumococcal disease is underestimated.
Certain groups are at high risk for invasive pneumococcal disease. These include young children, elderly individuals, patients with severe comorbidities, and people with substance abuse problems. The presence of chronic conditions in children and adults, such as cardiovascular disease (CVD), chronic obstructive pulmonary disease (COPD), asthma, renal disease, and diabetes mellitus (DM), increases the possibility of invasive pneumococcal disease.
What Is the History of Pneumococcal Vaccine Development?
- S. pneumoniae was recognized as the pathogenic cause of bacterial pneumonia in the 19th century by United States Army physician George Sternberg and scientist Louis Pasteur.
- In 1902, Friedrich Neufeld (a German scientist) discovered the “Quellung reaction” (a reaction caused by the capsule of the bacterium). It allowed the identification of various pneumococcal serotypes (variations in the bacterial species).
- Sir Almroth Wright supervised the first clinical trial of the pneumococcal vaccine. However, it was unsuccessful, and the vaccine's development was temporarily stopped for 30 years.
- In 1945, scientists developed the first polysaccharide (long-chain carbohydrate molecules) pneumococcal vaccine. Further, it was tested on a large population of Army officers.
- In 1977, a 14-valent (working against 14 serotypes) purified polysaccharide vaccine was approved in the US. It targeted the 14 serotypes that caused about 75 percent of the infections.
What Are the Modern Pneumococcal Vaccines?
Presently, polysaccharide and conjugate vaccines are administered in India. The pneumococcal vaccines include:
Pneumococcal Polysaccharide Vaccine (PPSV):
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PPSV23: It is a purified polysaccharide vaccine approved for use in the US in 1983 for children older than two years and adults. This is because PPSV has low immunogenicity (ability to invoke an immune response) in children younger than two years. The use of PPSV23 has consistently been shown to reduce invasive pneumococcal disease rates.
Pneumococcal Conjugate Vaccine (PCV): Each polysaccharide is conjugated to a carrier protein in PCV.
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PCV7: Conjugated vaccinations were developed for influenza and meningitis prevention. Hence, it led to the development and approval of a seven-valent pneumococcal conjugate vaccine for use in children in the year 2000.
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PCV13: In 2010, the vaccine was approved for children aged six weeks and older. It occurs when infants are at high risk of infection. PCV13 was specifically approved for the prevention of invasive pneumococcal disease and otitis media (middle ear infection). Furthermore, in 2012, the US FDA approved PCV13 for adults older than 50 years for pneumonia and invasive pneumococcal disease prevention. In India, PCV10 and PCV13 are currently available and being used.
What Is the Current Schedule for Pneumococcal Vaccines in Children and Adults?
There are different recommendations for pneumococcal vaccines for children and adults.
Children: There are multiple points to consider while proposing pneumococcal vaccination to a child. PCV10 and PCV13 protect against pneumococcal disease in India. PPSV is not used in infants as it has less efficacy in infants. PCV is injected into the thigh muscle in three doses. It is two primary injections and one booster dose at six weeks, 14 weeks, and nine months as a part of routine immunization.
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First Dose: The first dose is administered with the first dose of pentavalent vaccine (diphtheria, pertussis, tetanus, hepatitis B, and Haemophilus influenza type-B; Hib), oral polio vaccine (OPV), inactivated polio vaccine (IPV1), and rotavirus vaccine.
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Second Dose: The second dose is given at 14 weeks. It is combined with the third dose of the pentavalent vaccines (OPV, IPV2, and rotavirus vaccine).
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Third Dose: The PCV booster dose is administered at nine months, along with the first dose of the measles-rubella (MR) vaccine and the Japanese encephalitis (JE) vaccine (in endemic areas).
The advantages of PCV in children are long-lasting protection against pneumococcal disease, a reduction in pneumococcal transmission, and better indirect protection.
Adults: Many people usually get pneumococcal vaccination before the age of 19 years. However, according to authorities, adults who have never been vaccinated against pneumococcal disease should receive PCV15 or PCV20 if they are:
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65 years of age and above.
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19 to 64 years old with associated medical conditions.
If PCV15 is used, it should be accompanied by a subsequent dose of PPSV23. Adults who received a previous pneumococcal conjugate vaccine (PCV13 or PCV7) should discuss the available options with a vaccine provider to complete their pneumococcal vaccine sequence.
Adults 65 years and above can get PCV20 if they have already received the:
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PCV13 (but neither PCV15 nor PCV20) at any age.
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PPSV23 at or after the age of 65.
What Are the Challenges Faced by Pneumococcal Vaccine Providers?
The recent introduction of Hib-containing pentavalent, rotavirus, and IPV vaccines has given the experience to introduce other vaccines. However, some challenges faced by healthcare workers regarding pneumococcal vaccines are:
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The main challenge at the level of the health worker is to administer the three required doses (two primary doses and one booster dose) at six weeks, 14 weeks, and nine months of age with other vaccines at the same age.
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Adequate training for frontline health workers is essential for the smooth introduction of PCV at the community level.
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Reporting for PCV (mother-child protection card, vaccine records, tally sheets, and reporting coverage portals) requires attention at all levels. These interventions can strengthen the routine immunization system and increase PCV coverage.
Conclusion:
Current vaccine recommendations reflect the changes made over a short period. Moreover, efforts are required for newer vaccine development that has longer-lasting immunity effects with broader serotype coverage and works well for all ages. These include optimal growth conditions for bacterial capsule production for better output and lower cost. Furthermore, common pneumococcal proteins for broader coverage and immune adjuvants to improve immunity are advocated.
