Medical science’s finest gift to mankind


FROM conception to death, not even on a single day, is one completely free from the dangers of being affected by microorganisms. Practically, every day, we are repeatedly exposed to a wide variety of microorganisms – bacteria, parasites, fungi, and viruses, and many of them are highly infectious. They are able to bypass the first line of defense, enter our body, overcome the immune responses, multiply, and cause diseases that may have fatal end results, including permanent physical disabilities and/or even death. But fortunately, due to vaccination, prevention of life-threatening diseases has become highly achievable through immunizations that continue to save lives.
Vaccination represents a potent tool to prevent or contain infectious diseases that have high morbidity or mortality rates, by utilizing the immune (defense) system of the body. Scientific research shows that this represents the cooperative action of the innate (the natural or inborn) and adaptive (induced) immune systems. Thus, immunity is made of a multifaceted set of integrated responses involving a dynamic interaction of thousands of molecules that constantly work in unison to combat a microbial invasion. Understanding the role host immunity plays in response to vaccine antigens, and the chain of biochemical events that follow suite in providing relevant mechanisms of action of the immune system, thus, leading to providing lifelong protection, is simply, a miracle.
Most of the vaccines which are currently available were developed long before the era of molecular biology and biotechnology. They were obtained following experimental approaches leading to the inactivation of microorganisms, without any knowledge neither of the mechanisms and processes of diseases they were expected to protect from, nor of the immune responses triggered by the infectious agents, or by the vaccine itself. The past two decades have seen remarkable progress in the field of immunology and molecular biology, which have allowed a better understanding of the interactions occurring between microorganisms and humans. This basic knowledge has paved way for development of new vaccines for more safer and effective vaccinations. Production and deployment of vaccines is highly regulated and strictly governed. By standard requirements and practice, vaccines have to be subjected to stringent testing, trial, and screening processes to ensure their effectiveness, safety, stability, and that they are affordable. When the “requirements of a good vaccine” are satisfied, only then, are vaccines deployed for use in immunization programs.
The Centers for Disease Control and Prevention, Atlanta USA, has called immunization, and therefore, vaccination, the greatest public health achievement of the 20th century. Few measures in public health can compare with the impact of vaccination. It has significantly reduced disease, disability, and death from a variety of infectious diseases. When a child is born today, parents need not fear the scourges of smallpox, paralysis from polio, mental retardation and profound hearing loss from Haemophilus influenzae B meningitis, or any number of other frightening, often life-threatening infections, including, diphtheria, pertussis, tetanus, measles, mumps, and rubella. These vaccine-preventable diseases have been successfully reduced to negligible levels in developed countries, and in some cases, even in the developing world, including Papua New Guinea.
The invention of vaccination was the turning point in the war between microorganisms and humans. Although improved sanitation, hygiene, and antibiotics may have saved more lives, vaccines and vaccination represent the most cost-effective life-saving devise in human history. Vaccinations have transformed public health, particularly, since immunisation programmes first became properly established and coordinated in the 1960s. According to the World Health Organisation, many of the diseases that were previously responsible for the majority of childhood deaths have essentially disappeared. It has been estimated that 2-3 million lives are saved each year through current immunization programs.
The direct benefits of childhood vaccination in reducing the burden of disease morbidity and mortality in a cost-effective manner are well-established. In addition to saving lives, it has resulted in net economic savings and benefits to societies amounting to billions of kina. In the low- and middle-income countries, vaccination has resulted in savings due to reductions in costs of managing illnesses, leading to added economic benefits. By preventing episodes of vaccine-preventable diseases, vaccination also helps prevent associated out-of-pocket medical expenses, healthcare provider costs, and losses in wages of patients and caregivers. Studies have also strongly associated vaccines with numerous other positive effects beyond disease prevention. These include high intellect ability and educational attainment, long-term improved economic productivity, and enhanced fertility and reproduction.
The most ambitious aim of vaccination is eradication of disease. However, as long as any focus of infection remains in the community, the main effect of vaccination will be protection of the individual against infection. Vaccination serves to induce a ‘primed’ state of the body, whereby, the vaccine acts as the primary agent of infection, without causing disease. In response to primary infection, the immune system develops a memory capacity, in preparation, should there be any more future attacks. ‘Immune memory’ is one of the most fundamental combat strategies developed by the immune system, as a defensive measure against similar microbial invasion. Hence, in the course of actual encounter, the body responses in a rapid and robust manner with a series of biochemical events, leading to the destruction of the infectious microorganism before it causes disease.
Apart from providing individual protection, vaccination can also provide community protection by reducing spread of disease within a population. Person-to-person infection is spread when a transmitting case comes in contact with susceptible or vulnerable persons. However, if the transmitting cases come in contact with individuals who have immunity against the particular disease, then infection does not spread beyond the index case and is rapidly controlled within the population. Interestingly, this chain of human-to-human transmission can be interrupted, even if immunity coverage is not exactly hundred percent. This scenario is referred to as “herd immunity” or “community protection,” a profoundly important benefit of vaccination. Because of community protection induced by vaccines, persons who cannot be vaccinated, for example, those who have contraindications or are younger than the age for whom vaccines are recommended, can have an indirect protection against infection.
Although all vaccines are highly effective, some may fail to provide precisely a hundred percent protection. As a result, some individuals may fail to develop adequate immune responses upon vaccination, or even after an initial buildup of good immune responses, fail to sustain, and may eventually wane or drop to level considered not effective, making the person highly vulnerable. It is for these reasons that booster vaccinations are recommended, so to reinforce and sustain the immune responses. Fortunately, with the establishment of community immunity, such vulnerable persons are also being covered indirect. And so, achieving high vaccination coverage is important not only for individual protection but in preventing disease in vulnerable populations that cannot be directly protected by vaccination. This is one of the fundamental reasons and the rationale for advocating for immunization interventions to attain high population coverage.
Can a mere tablet, a drop of suspension, or a ‘jab’ protect us for a lifetime from specific microbial infections? Is it not weird and unreasonable to think so? Time and time again, it has been proven beyond any reasonable doubt that vaccination really does that which it is meant to do. And that is the wonder and miracle of vaccination – saving lives.
Sources: 1. Mims, C, et al. 1999, ‘Vaccination’, in Medical Microbiology, 2nd edn, Mosby, London, pp. 443-462; 2. Nandi, A and Shet, A 2020, Why vaccines matter: understanding the broader health, economic, and child development benefits of routine vaccination, Hum Vacc Immunother, 16(8), viewed 11 November 2021,; 3. Orenstein, WA and Ahmed, R 2017, Simply put: Vaccination saves lives, PNAS, 114(16), 4031-4033, viewed 11 November 2021,;4. Scudder, L 2013, The importance of vaccination, J Nurse Pract, 9(4), viewed 11 November 2021,

  • Gelinde Narekine is a technical officer with the discipline of Medical Laboratory Science, School of Medicine and Health Sciences, University of Papua New Guinea.