The BCG Conundrum
It's costing the government millions, yet a great horde is infected with TB. Is the vaccine really working in the way everyone thought it should?
By Sheila Alcantara, MD
His country is no less than a haven for disease-causing bugs of every type and sort. So ubiquitous have they become that it is no wonder infections consistently rank high among the greatest threats to the Filipino's health and survival. Even with the advent of powerful antimicrobials against a host of uncomplicated as well as life-threatening diseases, many people still succumb to age-old pathogens that have plagued the world for centuries.
Mycobacterium tuberculosis is one such specimen. Tuberculosis, the consumption, Koch's, or simply TB, has continued to wreak havoc especially on developing countries where environmental sanitation and poverty and the upsurge of HIV contribute greatly to the chain of transmission and reservoir of active cases.
Today, it is estimated that 15 million Filipinos are infected (Task Force on Tuberculosis, Philippine Practice Guidelines Group in Infectious Diseases. Pulmonary Tuberculosis: Clinical Practice Guidelines, 2000) and around 70 Filipinos each day die of tuberculosis (Philippine Health Statistics, 1998, www.doh.gov.ph). Virtually every patient that comes in with a chronic history of cough, even weight loss alone, is suspect, while thousands more run the risk of contracting the disease. The overall burden of this all-too-familiar malady can only be imagined, but the costs are staggering and the stakes high. Hence, control measures have since been adopted to lower its morbidity, and consequently lessen its impact not only on peoples, but also on governments as well.
The Vaccination Strategy
When a pathogen, or any of its components, is introduced into an organism, cells involved in the host's defense machinery react by recognizing the foreign entity as non-self, and stimulating the production of antibodies that are capable of attacking and destroying them. On subsequent exposure, so-called "memory cells" readily identify its reentry, thereby enabling the body to mount a faster and stronger immune response. Because of its potential in averting the occurrence of clinical disease, vaccines play a major role in the prevention and control of certain forms of infections.
In the case of the BCG, or Bacille Calmette-Guerin vaccine (named after those who developed it), a live but weakened strain of Mycobacterium bovis, a close relative of M. tuberculosis, is given through the skin, and is used to initiate protective immunity against the causative organism. Its efficacy against certain tuberculous infections has led to its extensive use all over the world, even in areas where TB is not endemic.
"In the Philippines, the use of the BCG vaccine started only less than three decades ago, in 1976, when it was launched with the implementation of the Expanded Program of Immunization or EPI," says Dr. Geraldine Crimen, medical specialist for the nationwide vaccination program on the Department of Health (DoH). She narrates that only infants two to 14 months of age in priority areas received the vaccine at first, and it was only two years later that they were able to expand the program countrywide. These days, the BCG vaccine can be administered even by local health workers.
With several million children already protected against TB since 1976, the layperson would expect a gradual decrease in its incidence, if not its ultimate eradication. Despite these preventive measures, however, there are still hundreds of thousands of walking TB time bombs, and there has been little change in its state in the past several years. Could it be that the vaccine is flawed, or was it believed to be something that it was not in the first place?
The Great Disclaimer
Vaccines for a variety of infections such as polio, tetanus, and measles, though not always 100-percent effective, prevent active forms of the disease as we know it. For example, the oral polio vaccine protects against the devastating illness notorious in causing paralysis via damage to nerves innervating muscle cells.
TB, on the other hand, is somewhat unique. After initially affecting the lungs, the tubercle bacilli are capable of spreading to distant sites in the body, like the brain, bone, kidneys, and intestines, producing such distinct clinical forms, as TB meningitis, Pott's Disease or TB of the bone, renal TB and TB ileitis. The main bulk of active TB cases in the country, however, is still the classical pulmonary TB, usually manifesting in the adult as cough of long duration, occasionally with bloody sputum, fever, and appetite and weight loss.
In the control drive against TB, however, vaccination with BCG has one primary objective: the prevention of TB meningitis. Dr. Crimen emphasizes that recommendations for the routine use of BCG by the World Health Organization were based on various studies proving its more consistent protection against TB meningitis. Hence, while BCG is effective against Mycobacterium tuberculosis, the causative agent of TB, thus far, it has only been shown to be effective specifically against blood-disseminated forms of TB such as TB meningitis, and not the more common pulmonary form of TB.
So far, the protective immunity against pulmonary TB is not definitive-"studies on its efficacy have actually been varied-some as low as ten percent,
yung iba zero pa nga, so it's not conclusive," says Dr. Crimen. She adds that "even WHO admits that it's really hard to say, that's why we're not coming out with any statement."
On the other hand, protection against the more complicated forms like TB meningitis and military TB has been consistently proved to be conferred by BCG vaccination. The EPI specialist even cites a local study conducted by Dr. Galicia of the University of the Philippines-Philippine General Hospital, which showed a 75 percent protective efficacy against TB meningitis.
The Case Against TB Meningitis
Potentially life-threatening, and perhaps, one of the most serious forms of TB known to man, TB meningitis exerts its dreaded invasion and subsequent destruction on the delicate protective coverings of the brain known as meninges. With time, the brain becomes inflamed and congested as well, and if the infection goes unchecked, dangerous increases in the pressure in the brain can eventually lead to death.
Hence, while the government spends around PhP30 million per year for BCG vaccination, it saves approximately Php70,000 per potential TB meningitis case that is otherwise not significantly prevented if not for BCG. This does not include the likely handicap and neurologic sequalae, such as developmental retardation, paralysis, and convulsions, which could cripple its survivors.
Indeed, while imperfect, vaccination with BCG still saves a lot of lives. In fact, latest data show a total of only 404 cases of TB meningitis for all ages in the Philippines for 2001 (Philippine Health Statistics, 2000, DoH) compared to the 449,460 symptomatic TB cases in the same year (National TB Control Program, 2001, DoH). While it can be said that it is still not enough, for now, there is no other, and despite its shortcomings, the benefits can just never be underestimated.
Moving Forward Despite TB
Perhaps, TB will be here to stay for a long, long while. But then again, maybe not. However, its rampant carnage of our people is totally despicable, and while its prominence in this society is decidedly multifactorial, one can only hope for the great discovery of the ultimate vaccine that can protect against the more common forms of this seemingly elusive disease. Until then, the battle will have to be fought…even with only what we have.
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