Our immune system is essential for our survival. Without an immune system, our bodies would be open to attack from bacteria, viruses, parasites and more. It is our immune system that keeps us healthy as we drift through a sea of pathogens.
This vast network of cells and tissues is constantly on the lookout for invaders, and once an enemy is spotted, a complex attack is mounted. The immune system is spread throughout the body and involves many types of cells, organs, proteins, and tissues. Crucially, it can distinguish our tissue from foreign tissue self from non-self. Dead and faulty cells are also recognized and cleared away by the immune system.
If the immune system encounters a pathogen, for instance, a bacterium, virus, or parasite, it mounts a so-called immune response. Everyone's immune system is different, but as a general rule, it becomes stronger during adulthood as, by this time, we have been exposed to more pathogens and developed more immunity. That is why teens and adults tend to get sick less often than children. Skin is the first layer of defence against external pathogens.
Once an antibody has been produced, a copy remains in the body so that if the same antigen appears again, it can be dealt with more quickly. That is why with some diseases, such as chickenpox, you only get it once as the body has a chickenpox antibody stored, ready and waiting to destroy it the next time it arrives. It is called immunity.
There are three types of immunity in humans including:
Innate immunity: We are all born with some level of immunity to invaders. Human immune systems, similar to those of many animals, will attack foreign invaders from day one. This innate immunity includes the external barriers of our body "the first line of defence against pathogens " such as the skin and mucous membranes of the throat and gut.
This response is more general and non-specific. In case the pathogen manages to dodge the innate immune system, adaptive or acquired immunity kicks in.
Adaptive (acquired) immunity: This protects from pathogens that develop as we go through life. As we are exposed to diseases or get vaccinated, we build up a library of antibodies to different pathogens. That is sometimes referred to as immunological memory because our immune system remembers previous enemies.
Passive immunity: This type of immunity is "borrowed" from another source, but it does not last indefinitely. For instance, a baby receives antibodies from the mother through the placenta before birth and breast milk following birth. This passive immunity protects the baby from some infections during the early years of their life.
However, immunization introduces antigens or weakened pathogens to a person in such a way that the individual does not become sick but still produces antibodies. Because the body saves copies of the antibodies, it is protected if the threat should reappear later in life.
This medical term 'immunity' became the buzz of the world since the vaccination drive was launched against COVID-19.
The original gap of 28 days between two doses was increased to 6 to 8 weeks for the Covishield vaccine and to 12-16 weeks (84 days) for Covaxin on 14.05.21.India, the world's largest vaccine producer, began the process with the indigenously developed Covaxin and Covishield vaccines. But both vaccines offered a different level of immunity against new coronavirus (SARS-CoV-2) or COVID-19 from Wuhan city of China in December 2019. This infectious disease spreads fast principally through droplets of saliva or discharge from the nose when an infected person coughs or sneezes was declared a pandemic by the WHO on 11.03.20.
With neither medicines nor vaccine, the killer virus spread like a tsunami across the world to 220 nations and territories to put humanity to test around the globe to make COVID a geopolitical challenge and health a geopolitical issue.
Vaccine: Under normal circumstances, making a vaccine can take up to 10-15 years because of the complexity of vaccine development. "Vaccines train our immune system to remember an infectious agent without our having to contract it," says Dr Michael Parry, chair of Infectious Diseases at Stamford Health in Stamford, CT.
"Thanks to advances in genomic sequencing, researchers successfully uncovered the viral sequence of SARS-CoV-2 in January 2020, roughly ten days after the first reported pneumonia cases in Wuhan. The ability to fast-track research and clinical trials was a direct result of this worldwide cooperation," said Dr Eric J. Yager, an associate professor of microbiology at Albany College of Pharmacy and Health Sciences in Albany.
"Vaccines help to build immunity and thereby reduce the probability of infection. The dosage and the duration between shots depend on the vaccine and the virus. As for COVID-19 vaccines, research shows that one dose is not sufficient to build enough antibodies. After the second dose, there was a good immune response," explains Dr K S Satish, senior consultant, pulmonology & chest medicine, Fortis Hospitals, Cunningham.
India, the largest vaccines producer in the world, developed Covaxin, the first indigenous vaccine, followed by Covishield in tune with its 'Go Corona Go' initiative.
Covaxin has been developed by Hyderabad-based Bharat Biotech International Ltd in association with the Indian Council of Medical Research (ICMR) and the National Institute of Virology (NIV). While Covishield, developed by Oxford-AstraZeneca, is manufactured by the Serum Institute of India (SII).
The gap between each vaccine dose depends a lot on the vaccines themselves. That is because the time intervals between dosages are decided based on the time for the immune system to generate antibodies with an increased affinity for the antigen. Each vaccine has its own ideal time between dosages.
Both vaccines following a two-dose regimen have shown more than satisfactory results since inoculation begun in India. The effectiveness of Covishield is nearly 90% as per global reports, while 81% of Covaxin as per interim 3rd phase trial results. The original gap of 28 days between two doses was increased to 6 to 8 weeks for the Covishield vaccine and to 12-16 weeks (84 days) for Covaxin on 14.05.21.
Covaxin was granted a restricted-use authorization in clinical trial mode. While Covishield allowed for restricted use in emergencies that can potentially prevent coronavirus infection in people aged 18 years and above.
People are confused about the vaccines because of the gap. That is why at Fit Northeast, we took it upon ourselves to enlighten our readers on the issue.