With the rapid spread of SARS-CoV-2, and the comparisons made between this virus and many others, it’s a common conception that eventually the population will develop some sort of immunity to the virus and life can return to normal. There are many experts who believe that because this virus is similar to other coronaviruses, there is no reason to doubt immunity is just around the corner.
However, since not much is known about whether or not immunity will develop, it’s dangerous to throw that sentiment around without having the scientific evidence to back it up. Furthermore, since there are several different types of immunity, it’s hard to determine which, if any, will apply to this particular outbreak.
What are the four types of immunity?
As mentioned above, there are several different types of immunity:
- Adaptive or acquired
Innate immunity is the immune system’s natural ability to fight off threats on a cellular level. Adaptive or acquired immunity occurs as we grow and the body is exposed to more threats. Adaptive immunity develops throughout our lifetime.
Passive immunity is a short-term level of immunity, achieved by borrowing antibodies from other sources, such as a nursing mother to her newborn baby. Immunisation immunity takes a weakened version of a pathogen and introduces it into the system so that the body can build up what is called an immunological memory to certain threats by creating antibodies that will be there if the pathogen shows up again.
What is acquired immunity?
Acquired immunity needs a lot of time to develop and grow so that it functions at its most optimal level. When a person is born, they are full of immune system cells designed solely to fight off infection from bacteria, germs or viruses. However, these cells need to be exposed to threats to help them grow stronger, thus strengthening the system as a whole. When this exposure occurs, the cells also create an immunological memory for certain pathogens and can save the information for when the threat comes back to strike again.
The cells that lead to acquired immunity learn how to target specific bacteria and viruses, and in the long run, this helps the body greatly when developing the immune system. Without acquired immunity, the body wouldn’t know which threat to target, and the immune system would suffer.
The difference between innate and acquired immunity
So, what is innate immunity? Innate immunity is similar to acquired immunity in the sense that every person is born with it, but it operates on a much different level. Innate immunity is a defence system in the body, but it doesn’t have the same ability to remember certain pathogens and target them specifically. The body’s innate immunity is designed to alert it to an unknown pathogen so that it can call on the cells to figure out what the threat is and what cells are needed to fight it off.
Both acquired and innate immunities need to work together to help fight off certain pathogens, but they have very different jobs within the body and thus, when each response kicks in, they lead to different results on a cellular level.
The efficacy of vaccines
Vaccines are a human-made level of immunity designed to help the natural immune system develop the cells needed to fight off otherwise deadly diseases. The World Health Organisation’s website lists 27 diseases that have vaccines to date.
Some on this list that have had particularly successful outcomes include:
- Hepatitis A, B, E
- Human papillomavirus
- Meningococcal disease
Vaccines work by introducing a certain pathogen (or its antigens) into the system so that it can develop an immunological memory for them. This memory, stored in the immune cells, then alerts the body when a threat is present, leading to a faster and more effective immune response.
Why is it so hard to develop a vaccine?
It may seem like a simple thing to do, but developing a vaccine can be incredibly difficult, involving years of trial and error. Aside from the vaccine needing to single out certain parts of the pathogen, such as a specific strand of RNA, certain viruses can actually mutate. When mutation occurs following the development of a vaccine, the specific RNA sample used to develop the vaccine becomes useless, because it is no longer the same as the one driving the virus.
Vaccine development can also be difficult because of the years it takes to get from development to public administration. Vaccines need to go through several steps prior to public release, and medical emergencies have often already died down in this time, either due to natural immunity or devastating results – thus halting research on the vaccine in question.