World Immunization Week 2020: How vaccines work to protect your health

The week from 24th to 30th April is observed globally as World Immunization Week. The aim is to raise awareness about and increase immunization against vaccine-preventable diseases. This year, the theme is ‘#VaccinesWork For All’ and the campaign’s focus is how vaccines and the people involved in their development and delivery are the heroes that protect everyone’s health. As COVID-19 rampages across the globe, nations are eagerly awaiting the arrival of a vaccine that will help keep the pandemic under control. While the hope is that a vaccine will be developed soon, it will likely take at least 12-18 months, given the complexities and regulations involved. [caption id=“attachment_4866911” align=“alignleft” width=“380”]  Representational image. Reuters[/caption] To commemorate World Immunization Week, here is a brief overview of how vaccines work and their contribution to global health.

How do vaccines work?

The human body responds to pathogens (disease-causing microorganism) by mounting an immune response. The white blood cells included in this immune response mainly include macrophages, B-lymphocytes and T-lymphocytes. Macrophages attack and engulf the pathogens and present antigens on their surface. They also release certain compounds called cytokines that cause inflammation. The lymphocytes use the antigens as identifiers to initiate a wider attack. They release antibodies that eventually overcome the infection. A type of lymphocytes, called memory cells, remain in the body even after the infection has subsided and are triggered should the pathogen attack again. This is what it means to have immunity against a disease; memory cells are activated without a delay and the person does not fall sick. Vaccines operate on similar principles; they imitate the characteristics of the antigens - without actually causing the disease - so the body is able to manufacture suitable lymphocytes that will swing into action should the pathogen be encountered in reality. Depending on the type of vaccine, multiple doses or booster shots may be required for full immunity. There are many different approaches to develop vaccines, many of which are being tried for COVID-19 as well:

• Live, attenuated vaccine: This is the classical form of the vaccine that is used for viruses and bacteria. A weakened version of the pathogen is cultured so that it is strong enough to provoke a reaction but weak enough to not cause disease. The MMR vaccine is an example of a live vaccine.
• Inactivated vaccine: As the name suggests, the virus or bacteria has been made inactive in this type of vaccine. The polio vaccine is an example - often these types of vaccines require booster shots.
• Toxoid vaccine: Certain bacteria release toxins in the body that can be deadly. Toxoid vaccines are a weakened form of these toxins that trigger an immune response to the toxins. The diphtheria vaccine is an example.
• Subunit vaccine: This type of vaccine only takes a part, or subunit, of the bacteria or virus to trigger an immune response.

The success of vaccines

According to the WHO, vaccines save over three million lives every year. In 2018, 86% of all infants received the three doses of the DTP-3 vaccine which protected them from life-threatening diphtheria, tetanus and pertussis. Since the development of the polio vaccine in the late 20th century, the prevalence of the disease has been massively dented in many parts of the world. Thanks to improvements in sanitation and immunization, the world has seen the number of deaths due to infectious diseases go down drastically. For more information, read our article on COVID-19 potential vaccines. Health articles in Firstpost are written by myUpchar.com, India’s first and biggest resource for verified medical information. At myUpchar, researchers and journalists work with doctors to bring you information on all things health.