Covid-19 Pandemic: Part 6: Understanding Vaccination, Immunization and Covid-19 Vaccines

Published in March 2022

In this paper we have explained in general what is the difference between vaccination and immunization and explained the terms of vaccine, immunity, vaccination, immunization, vaccine effectiveness, vaccine efficacy. Having done this, we have explained various vaccines available, their doses, modes of administration and other guidelines. We have then explained what mRNA vaccine is and how it differs from other vaccines and what is better in it. 

We discussed the historical context of Covid-19 pandemic, followed by the signs, symptoms and how it affects our body, various diagnostic tests, and the virus and its variants and general measures of protection. In this month’s edition we discuss vaccination, immunization and types of Covid-19 vaccines in our country.

Vaccination and Immunization are used interchangeably. But they are different technically. Let us understand these four terms:

Immunity: Protection from an infectious disease. If you are immune to a disease, you can be exposed to it without becoming infected. Immunity comes from taking a vaccine that protects against the disease or from the natural infection.

Vaccine: A preparation that is used to stimulate the body’s immune response against diseases. Vaccines are usually administered through needle injections, but some can be administered by mouth or sprayed into the nose. We now have vaccines to prevent more than 20 life-threatening diseases, helping people of all ages live longer and healthier lives. Immunization currently prevents 2-3 million deaths every year from diseases like diphtheria, tetanus, pertussis, influenza and measles. Covid-19 is the latest addition to the list. 

Vaccination: The act of introducing a vaccine into the body to produce protection from a specific disease. This is public health action and health service providers help the community to get vaccination

Immunization: A process by which a person becomes protected against a disease through vaccination. This term is often used interchangeably with vaccination or inoculation but technically this is our body’s response. Once a vaccine is introduced in the body (or the disease-causing agent introduced by natural infection) the body responds to it by developing antibodies and remembering the infection to fight in future. Largely we use immunization as the body’s response to vaccines rather than by natural infection.

The difference between vaccination and immunization is explained in the picture here. 

Vaccine Efficacy and Vaccine Effectiveness

Vaccine efficacy and vaccine effectiveness measure the proportionate reduction in cases among vaccinated persons as compared to non-vaccinated persons. Vaccine efficacy is used when a study is carried out under ideal conditions, for example, during a clinical trial. Vaccine effectiveness is used when a study is carried out under typical field (that is, less than perfectly controlled) conditions. Ideally, effectiveness should be the same as efficacy; practically, effectiveness will always be less than efficacy. Higher the effectiveness of the vaccine, less are the chances that the vaccinated person will get the disease. However, no vaccine is 100% effective and therefore, vaccinated people do have the chance of getting infected, but probability is very much less as compared to non-vaccinated persons. Vaccine effectiveness will also decline with time in most vaccines but not for all the vaccines.   

Covid-19 Vaccines

There are nine COVID-19 vaccines validated for use by WHO (given Emergency Use Listing). The first mass vaccination program started in early December 2020 and the number of vaccination doses administered is updated daily.  At the time when this goes to the press, 64% and 76% have one dose while 55% and 65% have been fully vaccinated with two doses in the world and USA respectively. 

Of the nine vaccines, there are only three that are used in the USA and two of them, Pfizer and Moderna, are mRNA vaccines while Johnson and Johnson is a whole virus vaccine. Table below details each of these three vaccines, approved age, type of vaccine, doses and additional doses and boosters are recommended or not and for what age etc. Pfizer and Moderna are the only vaccines fully approved by FDA and that too for age 12 and above for Pfizer and 18 and above for Moderna. Pfizer vaccine’s brand name is Comirnaty while Moderna vaccine’s brand name is Spikavax. Rest of them are approved under emergency use as of now. 

Table showing three vaccines used in USA with their types, doses and age recommendations
Vaccine Name	Approved for Ages in completed years	Type	Doses Needed in Primary Series	Time Between Doses	Is an Additional Dose Advised for Severely Immunocompromised?	Is a Booster Dose Recommended?
Pfizer	12+	mRNA	2	21 Days	Yes, at least 4 weeks after 2nd dose for certain groups	Yes, for anyone 12 or older ≥5 months after 2nd dose in primary series
Pediatric Pfizer	5-11	mRNA	2	21 Days	Yes, at least 4 weeks after 2nd dose for certain groups	No current recommendation
Moderna	18+	mRNA	2	28 Days	Yes, at least 4 weeks after 2nd dose for certain groups	Yes, for anyone 18 or older ≥5 months after 2nd dose in primary series
Johnson and Johnson	18+	Viral Vector	1	N/A	No current recommendation	Yes, for anyone 18 or older ≥2 months after first vaccination

Fully Vaccinated: Person is considered fully vaccinated after two weeks of the second dose of Pfizer or Moderna vaccine or after two weeks of a single dose Johnson and Johnson vaccine. 

What is mRNA (Messenger RNA) Vaccine and How Is It Different?

Pfizer and Moderna are the only two vaccines that are mRNA type vaccines and the rest all are Viral Vector vaccines. Unlike most vaccines who put a weakened or inactivated germ into bodies, mRNA vaccines created in a laboratory teach our cells how to make a protein or a part of it that triggers an immune response inside our body. That response, which produces antibodies, is what protects us from getting infected or diseased when the real virus enters our bodies. 

How does mRNA work?

Vaccines containing mRNA are given in the muscle of the upper arm. The mRNA will enter the muscle cells and instruct the cells’ machinery to produce harmless pieces of protein similar to protein present in Corona Virus called spike protein. Once this spike protein is produced, cells break down mRNA and remove it. These spike proteins are then displayed on the surface of the cells. Since they are identified as foreign, they trigger our immune system to form antibodies and activate other cells to fight off the infection. This is similar to what the body does when it actually gets an infection. So, by mRNA vaccine, the body learns how to protect against future infection from Covid-19 virus. The benefit of COVID-19 mRNA vaccines, like all vaccines, is that those vaccinated gain this protection without ever having to risk the potentially serious consequences of getting sick with COVID-19.

Do mRNA Vaccines interfere with the Genes in our body?

No, they do not. mRNA vaccines do not use live viruses and cannot cause Covid-19 infection. mRNA vaccine never enters the nucleus of the cell where our DNA is located, so cannot change or influence genes in any way. Neither mRNA, nor the spike protein produced by mRNA last long in the body. They get rid of it within a few days of vaccination after teaching the immune system how to fight against the infection. 

Is this mRNA technology new? Are the vaccines safe?

mRNA vaccines are newly available to the public but have been studied for decades and are not new to the scientists. FDA and Advisory Committee on Immunization Practices (ACIP) in the USA and Global Advisory Committee on Vaccine Safety (GACVS) have tested with the highest standard ethically and medically and approved the safety of the mRNA vaccines. No vaccine is completely risk free but the benefit of getting a vaccine far outweighs the risk of Covid-19 disease and its consequences.

Booster Dose

General recommendation for the second dose is to follow the same vaccine as the first dose. However, for the booster dose, you can opt for any vaccine, and it does not have to be the same vaccine. It is preferred to take the booster dose of mRNA vaccine rather than Jonson and Jonson vaccine. Everyone above the age of 12 are recommended to take a booster dose 5 months after the status of fully vaccination is achieved. 

Coming Up

Next month, we will discuss various other aspects of vaccines, importance of herd immunity, vaccine side effects, common questions and concerns related to vaccines and try to remove doubts in the minds of people related to the use of vaccines for Covid-19. We do see the declining trend of Covid-19 as of now and hope that it continues to decline, and another variant does not come up soon.