Our immune system is our defense against
diseases, and we have three types of it—innate, adaptive, and
passive. The innate immunity is the body's natural way to stop the
viruses or bacteria from entering the body. Passive immunity is the
type of immunity where we receive the antibodies from another source,
and it's usually short-lasting. And eventually, we
develop adaptive immunity as we grow
and get exposed to pathogens.

Another thing that helps us attain adaptive
immunity is the vaccine. When we see how quickly the novel
coronavirus is spreading, it's evident that we desperately need a
vaccine to help us with immunization.

How Do Vaccines Work?

Vaccines contain an agent that resembles the
microorganism of the disease in question. It's often made from
weakened or dead forms of microbes or its surface proteins. Once it
comes in contact with our immune system, the vaccine works as a
stimulant and trains the immunity to recognize the microbes as a
threat, fight and destroy it, but also to remember the microbes or
its surface proteins in the future.

Vaccination is the most effective way to fight
infectious diseases, and it helped us eradicate many diseases in the
past, for example, smallpox and measles.

Types of Vaccines

Conducting vaccination means that the person
that receives the vaccine shouldn't get sick. Scientists have
developed multiple ways of achieving this, which resulted in several
types of vaccines:

• 
  Live attenuated vaccines—The
  pathogen in the vaccine is weakened.
  
  
• 
  Inactivated vaccines—The
  pathogen in the vaccine is killed.
  
  
• 
  Subunit/conjugate—Only
  a part of the pathogen is administered.
  
• 
  Toxoid vaccine—Harmful
  toxins from bacteria are deactivated, and the deadly toxins are
  administered.
  
• 
  Conjugate—sugar
  molecules that cover the pathogen are linked to another pathogen's
  antigen, and the immune system recognizes the sugar molecules as a
  threat.
  
• 
  DNA vaccine—Still
  in development, the DNA vaccines contain a part of pathogen's DNA.
  
• 
  Recombinant Vector vaccine—Similar
  to the DNA vaccines, but these use a weakened pathogen as the DNA
  carrier.
  

Can Herd Immunity Help Against Coronavirus?

Herd immunity is defined as indirect
protections against the disease achieved when a large percentage of
the population becomes immune to it, be it from vaccinations or
previous infections.

Those who became immune can't spread the
disease further, thus protecting others who didn't get immunity. When
it comes to COVID-19,
there are two ways we can achieve herd immunity—with vaccination
and infection. This is where the problems arise.

It's not determined whether a person that was
already infected maintained immunity for future infections. Another
issue with COVID-19 is that a more substantial number of people would
have to become infected for humanity to develop herd immunity. We are
all aware that this would result in millions of people dying. That's
why the vaccine against COVID-19 is the best solution.

Coronavirus Vaccine Update

More than 140
teams of researchers are doing
their best to develop a safe vaccine against COVID-19. 129 vaccine
candidates are currently in the pre-clinical phase, which means they
are administered to animals.

Of these, 15 have reached phase one, and
they're administered to a small group of people. There are nine
vaccine candidates in phase two. These are given to hundreds of
people, helping the researchers learn more about safety and correct
dosage.

Phase three means a large-scale efficacy trial,
and there are only two candidates so far in this phase. None of these
is approved for general use so far.

Summary

Our immunity is the only thing that protects us
against diseases, but when the virus such as COVID-19 knocks on our
doors, the fear is justified.

The chances for attaining herd immunity are
small, as many people would have to fall ill, but luckily, there are
many ways a vaccine can be developed to help us fight the novel
coronavirus and win.