Vaccines — we are all in this together
by Ananya Malladi
Controlling, eliminating and eradicating diseases has always been a concerted effort. It takes a large network of resources, people and knowledge to develop and distribute vaccines. But why are vaccines so important and how do they work?
The basics: categories of vaccines
We cannot talk about vaccines without covering some of the basics. Since the 18th century, six broad categories of vaccines have been developed: live attenuated vaccines, inactivated vaccines, toxoid vaccines, recombinant vaccines, DNA vaccines as well as subunit and conjugate vaccines. Vaccine types can be further categorized according to method of administration:
- Monovalent vaccine: a single strain of antigen from the causative microbe to provide immunity against the disease (e.g.: Measles).
- Polyvalent vaccine: two or more strains of the same antigen to create immunity against a single disease (e.g.: Oral Polio Virus — OPV).
- Combined vaccines: a few antigens that can be combined without altering their properties are administered together to provide immunity from a variety of diseases (e.g. DPT).
The topic of vaccines is complex so here are a couple of resources to get you started on finding out more about the different categories:
- https://www.vaccines.gov/basics/types/index.html
- http://vaccine-safety-training.org/types-of-vaccine.html
Control, elimination and eradication of diseases
The journey of controlling, eliminating and eradicating a disease involves years of hard work and treating thousands of patients in hundreds of medical camps. Preventing the causative microbe from spreading and causing an epidemic, requires a series of planned steps to control, eliminate and finally eradicate the disease to reach the zero-patient goal.
First, reducing the occurrence and prevalence of a disease as well as the resultant morbidity and mortality is achieved by controlling the disease. The second step aims at eliminating the disease to zero occurrences in a geographic area through extensive interference. And finally, epidemiologists work on eradicating the disease in order to reduce the number of cases to zero worldwide. Eradication is the irreversible and permanent end of the disease. For example, smallpox, that had been around for at least 3,000 years, was officially eradicated in 1979. Once a vaccine was available, it took 183 years to eradicate smallpox.
What do we learn from the eradication of smallpox? Diseases spreading through a vector (like mosquito spreading malaria) are harder to control, eliminate and eradicate. Vaccinating healthy individuals and quarantining the sick is not enough as long as the infectious agent is alive in a carrier. The success of eradicating smallpox can be attributed to the short incubation period (visible symptoms occur four days after contacting the infection) and the unique and distinctive symptoms of the disease. This enabled epidemiologists to effectively implement isolation and treatment measures. Consequently, it took a synchronised series of steps worldwide between 1796–1979 to eradicate the disease.
An example
Caused by parasitic protozoans belonging to the Plasmodium family, malaria is spread through a carrier — female Anopheles mosquitoes. Common malaria spreading species of Plasmodium genus are P. falciparum, P. vivax, P. ovale, and P. malariae with P. falciparum causing most severe symptoms and which, if untreated, may result in death. Symptoms are observed 10–15 days after coming into contact with the disease. Signs of malaria include flu-like symptoms, fever, vomiting, shivering, nausea and joint pain among others.
Considering that there is no commercially available malaria vaccine, anti-malarial drugs and vector control are most effective for protecting and controlling the disease. Drugs such as Mefloquine, Doxycycline and Malarone are most commonly used for preventing malaria. Vector control involves the use of nets, indoor and out-door spraying or repellent creams. Health education and awareness programmes about the cause and effect of malaria infection are proven to be successful in reducing disease incidence.
What makes malaria eradicable? Once prevalent in USA and Europe, political will and financial support helped to drastically reduce the number of cases. Similar political and financial resources support the African Leaders Malaria Alliance (ALMA) to achieve their goal of eliminating malaria in Africa by 2030. The short course of the disease, extensive preventive measures and effective drugs make the eradication of malaria plausible.
Immunization is the most effective and economic health initiative. Over the last few decades we have witnessed the successful eradication of smallpox and a decline in the deaths caused by diseases like polio, diphtheria, tetanus, whooping cough or measles. We have recorded unparalleled advances in discovering new vaccines. Announced as the decade of vaccines (2011–2020) by UNICEF, polio vaccination reduced the number of cases by more than 99% and is on its way for global elimination. The Initiative for Vaccine Research (IVR) by the WHO and similar organisations focus their research efforts on developing new vaccines to protect people in economically burdened countries.
Like a successful orchestra performance, the control, elimination and eradication of diseases takes years of hard work and preparation, and requires a synchronised series of steps on a global scale.
