VACCINES- THE TALK OF THE TOWN

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The fight between the humans and pathogens is an ancient one with both emerging victors at different times. In older times, a lot of people died of infectious diseases with small pox being one of the biggest villains. Almost 35% of the patients who contracted the severe form of the virus died of the infection. Another example is the Spanish flu of 1918. It is one of the most dangerous pandemics humanity has ever encountered killing around 50 million people worldwide!!!

In constant endeavour to fight these infections, humans experimented in a number of ways. In the case of small pox, it was observed that a person who had been previously infected with a similar virus, cowpox, developed immunity against small pox. That observation brought about a medical revolution and led to the birth of what we call today, VACCINES. The terms vaccine and vaccination are derived from Variolae vaccinae known as the cow pox. This is because this was from where the first vaccine for small pox was made by the English physician and scientist, Edward Jenner. Beginning from the crude method of deriving material from the cow pox lesions from a patient and inoculating it onto the patient requiring treatment for small pox to the modern day mRNA vaccines, the developments in the fields of immunology and vaccination have come a long way saving millions of lives around the world.

Now the million dollar question is, “How does a vaccine confer immunity?” To understand this, it is necessary to understand the basics of how our immune system works. Our body has developed an elaborate system of fighting off foreign invasion by developing a quick and coordinated fight against the invader. This is called an immune response. Any foreign substance or a toxin that is capable of inducing an immune response, especially the stimulation for production of antibodies, is called an antigen. When the body is presented with an infection for the first time, it produces antibodies that are specific to fight the particular infection. This leads to the development of immunological memory, a unique feature of adaptive immunity. Now subsequent exposure to the same infectious agent will mount an immediate and stronger response thus providing the individual required immunity against it. This is the basic principle on which vaccinations work. I know I try to make it sound very simple but in fact it is not. The patients have a lot of apprehensions about the administration of these vaccines to their babies and also themselves. One can always get their doubts cleared by talking to a specialist. Thanks to the modern technology, it is now possible to have an online consultation and address all your concerns without even stepping out of the house.

There are different types of vaccines depending on the type of inoculation employed. These are:

Live attenuated Vaccines

Live attenuated vaccines which use the live form of the pathogen responsible for the disease but in a weakened state and hence incapable of infecting the host. The host produces the antibodies and develops the immunologic memory thus conferring immunity. Examples of this type of vaccine include:

  • Measles, mumps and rubella
  • Rotavirus
  • Small pox
  • Chicken pox
  • Yellow fever
  • Oral polio vaccine

Inactivated vaccines

Inactivated vaccines used the killed version of the microorganism responsible for the disease. These do not provide as good immunity as the live vaccines but also carry less danger of infecting the person receiving it. These therefore require periodic booster shots. Examples of this type of vaccine are:

  • Hepatitis A
  • Flu (shot only)
  • Polio (shot only)
  • Rabies

Subunit, recombinant, polysaccharide and conjugate vaccines

Subunit, recombinant, polysaccharide and conjugate vaccines use the chemical component of the causative microorganism that elicits the immune response rather than the entire microorganism. This can be protein, sugar or capsid (protective covering around the microorganism). This type of vaccines elicit a very strong immune response and can be used on all kinds of people including old patients and those with compromised immunity. Examples of this type of vaccine include:

  • Hib (Hemophilus influenzae type b) disease
  • Hepatitis B
  • Human papillomavirus
  • Whooping cough (part of the DTaP combined vaccine)
  • Pneumococcal disease
  • Meningococcal disease
  • Shingles

The latest addition to the type of vaccines is the modern day mRNA vaccine developed for COVID 19. mRNA, also called messenger RNA, directs the formation of protein inside the cell. In the latest COVID vaccine, the protein targeted is the spike protein which gives coronavirus its characteristic shape of a crown and from where the name of the virus is derived. The body produces antibodies in response to this protein without getting infected thus becoming immune to the virus. mRNA vaccine has the advantage of developing at increased speed when compared to the conventional types of vaccines that normally take 10 to 15 years to come to the market since inception. The extraordinary circumstances that the present pandemic has created have forced the countries around the globe to come out with a vaccine as early as possible. In the U.S., everyday around 2000-3000 people are dying which is more than the lives lost in the attack of 9/11!! President Donald Trump came out with a vaccine development program called “Operation Warp Speed” to quicken the process of developing a safe and effective vaccine at record speeds to halt the virus that has caused a tumultuous turn in the course of humanity.

These days, every Monday has become a Good Vaccine News Day, with pharmaceutical giants round the globe announcing the development of vaccines at record speeds. After Pfizer/BioNTech and Moderna vaccines which are the mRNA variants, the latest development came from the UK-produced Oxford University/AstraZeneca vaccine having almost 90% efficacy depending on the dosage used. The good thing about the Oxford vaccine is that it doesn’t require the stringent conditions that are necessary to preserve Pfizer and Moderna vaccines. Also the Oxford version is a cheaper one costing at around $4 per dose while the former cost around $26 a dose. Now the biggest challenge for all the countries is to ascertain the efficacy of the vaccines and once found to be satisfactorily efficacious, to ensure equitable distribution among its citizens irrespective of their economic and social conditions. Beating the virus is the ultimate goal and this time it seems that the opponent has come with quite tough preparation equipped with the necessary arsenal at its disposition. Finding a chink in the armor isn’t that easy this time around and requires a strategy that circumvents the normal thought processes. The virus is intelligent than the most intelligent species on earth this time and any lowering of the guard by humans is going to have profound consequences on all fronts for which the repercussions are surely to be felt for decades to come.


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