Vaccine against invasive pneumococcal disease
Specialist underscores efficacy, safety, and cost-effectiveness of Prevenar
There is an organism, which, when it causes a disease, can go by unnoticed, but in fact can actually be deadly. And it goes by the name of Streptococcus pneumoniae.
Statistics show that pneumococcal disease causes around 1.6 million deaths worldwide, mostly in infants and young children. In developing countries like the Philippines, it is the cause of one in every 10 deaths in infants.
"Invasive pneumococcal disease (ipd) is only one type of presentation of pneumococcal diseases," explained Dr. Jaime Santos, pediatric-infectious-disease specialist at the Philippine Children's Medical Center, when he spoke at the 18th postgraduate course at the Far Eastern University in October. A person can get infected by Streptococcus pneumoniae through the transmission of tiny droplets coming from an infected individual.
Once in the nasopharynx, the organism can travel to various parts of the body, and can result in health problems of varying severity. It can be aspirated into the lungs and cause local pneumonia; to the middle ear and cause acute otitis media; spread through the blood and cause sepsis; and to extrapulmonary sites and cause empyema. These diseases are collectively termed as ipd.
Patients and "carriers"
However, not all those with Streptococcus pneumoniae lurking within their nasopharynx will actually manifest symptoms of any of the above diseases; they could be "carriers." However, these carriers can spread the organism to others who may end up being infected.
What is alarming in the statistics regarding this disease is that mortality rates are particularly high among the very young. Local ipd deaths have been recorded, and some show 90-percent mortality in children below five and 78-percent mortality in those under two. In terms of carrier states, a local study done showed isolates of Streptococcus pneumoniae in blood cultures from the nasopharynx of children under one. This means that the most common ipd carriers are also young infants. These young carriers also cause an increase in the incidence of pneumococcal disease in adults living with them. Thus, it is this population who should be the primary target for protection.
Vaccine-preventable
"Pneumococcus is actually one of the most common vaccine-preventable deaths," said Santos, as he went on to explain the benefits of vaccination against ipd. Although vaccination has been available, people need to realize its value in routine use. The heptavalent pneumococcal conjugate vaccine (Prevenar), in particular, has been shown been to be highly effective in inducing immunity in the younger population (most especially in those below two years of age). The vaccine was licensed in the US in 2000, and introduced in the Philippines last year.
In randomized controlled studies, the heptavalent vaccine showed an 80- to 94-percent efficacy in protecting children from pneumococcal disease. This was supported by the data collected by the US Centers for Disease Control and Prevention (cdc) the year after the vaccine had been first used (1996). The rates of ipd were shown to have a decreasing trend along with pneumonia and otitis media caused by pneumococcus. Nasopharyngeal carriage, as well as infection with antibiotic-resistant strains, was also reduced after vaccination. Immunizing the infant population has also resulted in a decrease in pneumococcal-disease incidence in adults-a sign of "herd immunity."
Cost-effectiveness and recommendations
In terms of cost-effectiveness, vaccination prevented 38,000 cases of ipd in children alone with a cost of US$112,000 per life-year saved, based on the 2000-2004 data gathered by the cdc. Considering the herd immunity in the prevention of disease in adults, it prevented 109,000 cases, bringing down cost to US$7,500 per life-year saved.
So who should be vaccinated? The vaccine should be administered to all children who are below two years old. High-risk populations should also be included on the list: those with congenital immune deficiency, chronic cardiac and pulmonary diseases, cerebrospinal-fluid leaks, renal insufficiency, diabetes, or immunosuppression.
The current recommendation for the administration of the heptavalent pneumococcal conjugate vaccine (Prevenar) is at two, four, and six months, followed by a booster dose at 12 to 15 months. M Cherrie Cruz
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