A Brief History of Vaccination
Posted on : August 5, 2019 by Clinic One on blog
“Prevention is better than cure.” One of the most effective process of prevention against certain infectious diseases is through vaccination. The World Health Organization (WHO) has defined vaccine as “biological preparation that improves immunity to a particular disease”. Vaccine contains a component that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microorganism, its toxins or one of its component proteins. The vaccine stimulates the body’s immune system to recognize the agent as foreign, destroy it, and “remember” it, so that the immune system can more easily recognize and destroy any of these microorganisms in future encounters. Prevention of disease has been one of the major goal of modern disease.
Initial vaccine development attempts date back to 1796 AD when Edward Jenner invented a method to prevent Small Pox. The first vaccine consisted of material taken from the blister of a Cowpox patient. Routinely administered vaccines were produced in industrial scale in early 20th century. Initial vaccines included pertussis vaccine (1914), diphtheria (1926) and tetanus (1938). These three vaccines were combined to form DPT in 1948 and administered through a single injection. Before 1955 polio used to cause epidemics and resulted in lifelong disabilities in patients. Polio vaccine was licensed in 1955 and with its widespread use polio is in the brink of eradication. The latter half of 20th century saw development of multiple vaccines like measles, mumps, rubella, Hepatitis B, Hemophilus influenza type B. As the new vaccines are being developed, the vaccination schedules have been revised accordingly. Nepal started its pilot vaccination program in 1979 with DPT, tetanus and measles. From 1989 the program has been expanded to whole country with an aim of universal vaccination in children. There is no schedule for adult vaccination in Nepal from National Health policy/program.
Human body is protected against infections by immune system. Immune system works by recognizing and removing infection causing agents like bacteria and virus. These functions are achieved by special immune cells and antibodies. Antibodies are proteins that help to eliminate the microorganisms and subsequently help the patient to recover. Immune system also develops memory to eliminate or fight off the offending agent in future encounters. The next time a vaccinated or previously infected person is exposed to the organism, the immune system detects and produces the antibodies to eliminate the infection. This response protects the person from disease development. For example, if a person develops a viral infection called Mumps, he or she will be protected from mumps virus for entire life.
Vaccines work by creating a memory for immune system. This memory will be utilized to create antibodies to fight infection. Although the vaccine may contain weakened or killed forms of the microorganism, its toxins or one of its component proteins, the vaccinated person will not develop the disease. Vaccines have proved to be safe and highly effective method of disease prevention. In recent times there have been concerns regarding safety of vaccination. But the benefit of vaccination distinctly outweigh the risks. Benefits of vaccine is evident by the decreasing number of patients with infections against which population based vaccination was carried out like polio, diphtheria. Vaccines have been created to make our life easier.
Remember the last flu which had you down for days. The same flu can kill a person especially infants, elderly and patients with reduced immunity. A vaccine against Influenza virus can significantly decrease the chance of acquiring flu and preventing days of suffering.
Vaccines are important as they protect the recipients from becoming sick due to infection. Vaccinated persons are likely to get a milder form of disease if they happen to be infected. Infections are also less likely to spread in community if there is universal vaccination.
The age groups for receiving vaccines have been divided as Children and Adult. Children vaccination usually done as per the country’s policy for immunization. Additional vaccines, which are not administered by Government, can be administered at privately owned clinics. Examples of these types of vaccines include Rota Virus, Hepatitis A, Meningococcal
For adults, different countries have drafted their own schedule. For healthy adults, the Centers for Disease Control and Prevention (CDC), USA recommends Influenza, Tetanus, Diphtheria, Pertussis, Measles, Mumps, Rubella, Varicella, Zoster, Human Papilloma Virus, Pneumococcal and Meningococcal vaccine based on previous immunization status, age group and gender. For details regarding vaccines in adult, reader is suggested to consult a doctor.
Other special groups are required to have different set of vaccines for optimum protection. These groups are
- Health care workers
- Travelers to certain countries
- People who inject drugs, men who have sex with men
- Residents of long term care facilities like nursing homes
There are four types of vaccine:
- Live-attenuated vaccines: These contain weakened microorganisms which cause a disease. As vaccination with these vaccines resemble natural infection, the resultant immunity is strong and long lasting. The vaccine can act differently in patients with weak immune system and organ transplant recipients. Patients with these condition must consult their health care provider before getting vaccinated. Examples of live vaccine include Measles, mumps, rubella (MMR combined vaccine), Rotavirus, Smallpox, Chickenpox, Yellow fever. These vaccines should be stored in refrigerator until administered making them difficult to transport in remote and resource limited places.
- Inactivated vaccines: Vaccines with killed microorganisms are called inactivated vaccine. These provide weaker response when compared with live attenuated vaccine. These vaccines require booster doses to maintain immunity. Inactivated vaccine include Hepatitis A, Flu shot, Polio shot and Rabies.
- Subunit, recombinant, polysaccharide, and conjugate vaccines: These vaccines contain certain components from the microorganisms. These component can be protein, sugar or part of the capsule (the outer covering of the microorganisms). These produce a strong immunity which may sometimes need booster doses to maintain the protection. These are safe even in organ recipients and persons with weak immunity. Examples include Hib (Haemophilus influenzae type b), Hepatitis B, HPV (Human papillomavirus), Whooping cough, Pneumococcal disease, Meningococcal disease, Shingles.
- Toxoid vaccines: Toxoid vaccines contain toxin produced by the microorganisms. The immunity obtained by vaccination with toxoid vaccine is directed against the toxin of the bacteria or virus. Examples of toxoid vaccine are Diptheria and Tetanus Vaccine.
Different countries have developed their own immunization schedule based on prevalent infections, vaccine availability and at risk population. Nepal Government has been implementing National Immunization Programme through Child Health Division of Department of Health Services (DoHS). Children under 5 years of age and pregnant ladies are routinely vaccinated. Following are the vaccines routinely administered in Nepal.
- Bacillus Calmette Guerin (BCG): Tuberculosis is common in developing and under developed nations. It is caused by Mycobacterium tuberculosis bacteria. BCG has history of 80 years and it is one of the most widely used vaccines. Approximately more than 80% neonates and infants receive this vaccine in countries where it is part of the national childhood immunization programme. This vaccine protects against meningitis (infection of layers covering the brain) and disseminated tuberculosis in children. It is administered at birth by injecting the vaccine into the skin.
- DPT-HepB-HiB: This combination vaccine contains Diphtheria, Pertussis, Tetanus, Hepatitis B and Haemophilus influenzae type b. Three doses are injected in the muscle through skin at the age of 6 weeks, 10 weeks and 14 weeks each.
Diptheria: Bacterium causing Diptheria infects throat and releases toxin into blood stream. The toxin can cause damage to nerves, brain or heart. It is transmitted from one person to another through droplets expelled during coughing or sneezing.
Pertussis: Pertussis is also called Whooping Cough. It is spread through droplets or by direct contact with infected throat or nasal discharges. It is caused by a bacterium, Bordetella pertussis. It can cause serious illness in infants and patients with weak immunity.
Tetanus: Tetanus is caused by the toxin produced by the bacteria which infects a wound. The bacterium is found in soil and the intestinal tracts of certain mammals. A wound is infected by tetanus bacterium after being exposed to soil or animal excreta. The bacterium then multiplies in the wound and releases toxin. The toxin affects the nerves.
Hepatitis B: Hepatitis B virus infects and damages the liver. It is transmitted through the contact with an infected person’s body fluids (during unprotected sexual intercourse, the sharing of needles during injection drug use or contact with contaminated blood or blood products) or during child birth from an infected mother to her baby.
Haemophilus influenzae type b: Hemophilus influenzae is a baceterium which can cause serious disease in children and in adults with weak immunity. Haemophilus influenzae type b can cause meningitis, pneumonia, infections of joints, covering of the heart and can result in death.
- Polio: Caused by Polio virus, Polio or Poliomyelitis causes crippling and life threatening disease. The virus affects brain and spinal cord causing damage to nerves. There are two types of polio vaccine 1. Oral vaccine: given through mouth as drops and 2. Inactivated Polio Vaccine administered as an injection. In Nepal, oral drops are administered as three doses at 6, 10 and 14 weeks. Inactivated vaccine is administered at 14 weeks of life.
- Measles-Rubella (M-R): Vaccine for both diseases are administered in a single dose. Measles is caused by virus. It causes rash, fever, and cough and the complications include infection of ear and lungs. Rubella, also known as German measles, is a mild viral infection. If mother is infected during pregnancy, it can cause severe birth defects in the child. The M-R vaccine is administered at 9 and 15 months.
- Japanese encephalitis: Japanese encephalitis virus is main cause of viral encephalitis especially in Asia. When encephalitis develops upto 30% of patients are likely to die and permanent neurologic or psychiatric sequelae can occur in 30%–50% of those with encephalitis. Japanese encephalitis vaccine is given at 12 months.
Pregnant ladies are recommended to receive tetanus and diphtheria shots. Two doses are given one month apart during second trimester of pregnancy.
Two vaccines that are recommended for healthy adults are Pneumococcal Vaccine and Influenza.
Pneumococcal: Pneumonia is an acute respiratory illness caused by lung infection. It can be fatal in elderly persons and persons with weak immunity. Pneumococcal vaccine protects from the pneumonia caused by the bacterium Streptoccocal pneumoniae.
Influenza: Influenza virus causes flu which is highly contagious. Simple flu can be distressing with loss of productivity. It can cause serious complication like pneumonia. Influenza vaccine is administered as injection into muscle and the vaccine should be repeated every year.
People are worried about adverse effects of vaccines. Most of the vaccines are safe and have no side effects. Side effects due to vaccines are minor and transient. These include mild fever, mild rash, headache and body aches. Rarely serious allergic reactions can occur.
Other than Government administered child vaccination, there are limited number of clinics and hospitals offering other vaccine and adult vaccines. Clinic One has been established as a preventive clinic in Lalitpur. With international standards, it is one of the best vaccination center in Kathmandu valley. It has similar pricing for Nepalese and foreigner. It has been providing vaccinations for both adults and children. It has been providing cost effective and prompt preventive medical services.
For more information about the Vaccines available at Clinic One, Click Here
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