The role of vaccines in protecting humanity is unprecedented. Covid-19 is probably the best example that we have witnessed live and have been able to understand the importance of vaccines. Earlier also, vaccines have helped protect us from numerous diseases such as smallpox, polio, ebola, chickenpox, tetanus, whooping cough, rubella, mumps, measles, diphtheria, hepatitis A and B, pneumococcus, rotavirus, meningococcal disease and haemophilus influenzae. There are also vaccines for typhoid, dengue, rabies, meningitis A, cholera, yellow fever, and Japanese encephalitis.
Even though the list of available vaccines seems quite comprehensive, there are still dozens of diseases that have either no vaccines or have ones that are only partially effective. It makes us wonder why not all diseases caused by viruses, bacteria, parasites and other microorganisms can be protected through vaccines. To understand that, here are some reasons why we don’t have vaccines for every disease.
Lack of funding – There’s usually significant investment required to develop a vaccine. Covid-19 vaccines are an exception, as they were developed on an emergency use basis. Vaccine development typically takes several years to determine its safety in the long term. In case of Covid vaccines, their long term safety is yet to be determined. Since vaccine development could stretch into several years, it needs significant amount of funding. And in case there are medicines available that are much cheaper, pharmaceutical companies don’t find it appropriate to develop a vaccine.
Diversity of microorganisms – Just like everything else, vaccine technology too has its limitations. Most vaccines work by creating antibodies to block the targeted disease. These anti-bodies are essentially Y-shaped proteins that block the binding proteins of the disease. But vaccines can’t be for all diseases, as bacteria are known to have up to 6,000 types of target proteins. It’s nearly impossible to have a vaccine to block each of these target proteins. Parasites are known to have even a higher number of binding proteins.
Tricky and tough microorganisms– Another problem is that some viruses mutate at a very fast pace. So by the time a vaccine is created, it may no longer be effective, as the basic surface of the virus has changed. This is why we don’t have any effective, long-lasting vaccine against diseases like flu, malaria, HIV and tuberculosis. HIV is among the fastest mutating viruses known to humankind. Tuberculosis bacteria are so resilient that they can survive even when trapped by white blood cells. The malarial parasite keeps changing shape, making it difficult to create a long-lasting vaccine against it.
However, we need not lose hope, as researchers are working on new technologies that can help make vaccines much faster. With the use of DNA and RNA platforms, vaccines are expected to be developed much faster. Advanced simulation techniques based on human body and genetics will enable us to evaluate long-term safety of these vaccines as well.