COVID-19 Vaccine Update

COVID-19 Pandemic has shown the world the importance of staying healthy. Undoubtedly, vaccines are one of the most effective tools to prevent diseases and death within human population.

The world is still amidst a COVID-19 pandemic and our only ray of hope are vaccines, as getting vaccinated has the potential to save millions of lives each year. They work by training and preparing the body’s natural defences – the immune system – through simultaneously recognizing and fighting off the viruses and bacteria they target. After vaccination, if the body is later exposed to those disease-causing germs, the body is immediately ready to destroy them, preventing illness and death.

The Immune System – Body’s Defense against Infections

To understand how vaccines work, it is important to first look at how our bodies generally fight illnesses. When germs, such as bacteria or viruses, invade the body, they attack and multiply. Specifically, this invasion, called an infection, is what causes illness. The immune system of our body uses a myriad of tools to fight such infections. Primarily, the white cells consisting of macrophages, B-lymphocytes and T-lymphocytes destroy the bacteria or virus. Some people believe that naturally acquired immunity – immunity from having the disease itself—is better than the immunity provided by vaccines. However, natural infections can cause severe complications and can be deadly. Thus vaccination is the best way to prevent them as compared to letting our natural immunity fight against such diseases.

Types of Vaccines

• Live, attenuated vaccines: These vaccines contain a version of the respective living virus or bacteria that has been debilitated in a way so that the virus does not cause any serious illness in people with healthy immune systems. Live, attenuated vaccines are similar to a naturally occurring infection. Even though they are highly effective, not everyone can receive these vaccines. For instance, children with weakened immune systems and people undergoing chemotherapy – cannot get live vaccines.
  

• Inactivated vaccines: These are made by killing or inactivating the germ during the process of vaccine creation. Often time, multiple doses are necessary to build up or maintain immunity.

• Toxoid vaccines: They prevent diseases caused by bacteria that produce toxins in the body. In the process of making these vaccines, the toxins are weakened so they cannot cause illness. Weakened toxins are called Toxoids.
  

• Subunit vaccines: This vaccine only includes parts of virus, bacteria, or subunits instead of an entire germ. Since these vaccines only contain the essential antigens and not all molecules, side effects are less common.
  

• Conjugate vaccines: Such vaccines fight a different type of Bacteria with polysaccharides as antigens. Specifically, this linkage helps the immature immune system to not only react to the coating but also helps in the development of an immune response.

Specifically talking about the SARS-CoV-19 we have different types of vaccines with varied levels of efficacy.

As of April 2021, 13 vaccines have been authorized:

mRNA vaccines

• • Pfizer–BioNTech vaccine
  • Moderna vaccine

5 conventional inactivated vaccines

• • BBIBP-CorV
  • Corona Vac
  • Covaxin
  • WIBP-CorV
  • CoviVac

4 viral vector vaccines

• • SputnikV
  • Oxford–AstraZeneca vaccine
  • Convidecia
  • Johnson & Johnson vaccine

2 protein subunit vaccines

• EpiVacCorona
• RBD-Dimer

 In total, as of March 2021, 308 vaccine candidates were in various stages of development, with 73 in clinical research, including 24 in Phase I trials, 33 in Phase I–II trials, and 16 in Phase III development.

Usually, it takes approximately ten years to develop an effective vaccine, but all these first-generation vaccines have a year old immunogen and are all EUA (Emergency use authorization).

VACCINATION – IS A MUST?

We have a virus that has been constantly mutating for last one year. As on date, there are thousands of different variants, however only a handful of them are worthy of concern. These “Variants of Concern” (VoC) are directly linked to the evolution and survival of viruses. Over time, these VoC’s have become highly efficient in transmission and thus are capable of reinfection in previously infected people as few persons have been vaccinated worldwide resulting in a large susceptible pool of population for the virus to infect, replicate and mutate.

Even though, the effect of the VoC’s on the first generation of COVID-19 vaccines has been mixed, however, the available data illustrates that the present vaccines might still be sufficient to protect individuals against COVID-19, or at least severe COVID-19. Modifying present COVID-19 vaccines is the need of the hour and gladly work has already been started to protect against variants. Safe and effective vaccines are game changer: but for the foreseeable future we must continue wearing masks, maintaining physical distance, and avoiding big and large gatherings. Undeniably, vaccinations are the rays of light at the end of the tunnel however, being vaccinated does not mean that we can throw caution to the wind and put ourselves and others at risk.

Holistically, looking at the infection rate and the vaccination data, studies suggest that infections are very low after vaccination. However, looking at a bigger picture, getting the vaccine is one of our best options to collectively survive this pandemic. Please continue to do your bit. Do not let your guard down. Do not fall victim to the pandemic fatigue.

Co-authored by:

Dr. A. K. Dewan
Director – Surgical Oncology

Dr. Neelam Sachdeva
Sr. Consultant – Microbiology &
Infection Control Officer