What is a vaccine?
As a type of biological compound, it can induce immunity in the body of a person who receive it.
This treatment aims to stimulate the body’s immune system to fight with infectious pathogens such as bacteria and viruses.
How to use:
They are often injectable (intramuscular or subcutaneous and intradermal) and sometimes use orally (such as polio). In most cases multiple injections are needed to achieve complete and permanent immunity.
Vaccine classification based on microorganism type:
attenuated live vaccines (BCG), inactivated vaccines (pertussis, typhoid, cholera), toxoids (diphtheria, tetanus) and polysaccharide vaccines (meningococcus).
Viral vaccines: attenuated vaccines (oral polio, rubella, measles, mumps, yellow fever), inactivated vaccines (influenza, injectable polio, rabies), recombinant vaccines (hepatitis B)
Vaccine classification based on production technology:
Generally, three techniques are used to produce the vaccine:
- The whole-microbe approach
- The subunit approach
- The genetic approach (nucleic acid vaccine)
The genetic approach (nucleic acid vaccine)
Unlike vaccine approaches that use either a weakened or dead whole microbe or parts of one, a nucleic acid vaccine just uses a section of genetic material that provides the instructions for specific proteins, not the whole microbe. DNA and RNA are the instructions our cells use to make proteins.
In our cells, DNA is first turned into messenger RNA, which is then used as the blueprint to make specific proteins.
A nucleic acid vaccine delivers a specific set of instructions to our cells, either as DNA or mRNA, for them to make the specific protein that we want our immune system to recognize and respond to.
The nucleic acid approach is a new way of developing vaccines. Before the COVID-19 pandemic, none had yet been through the full approvals process for use in humans, though some DNA vaccines, including for particular cancers, were undergoing human trials. Because of the pandemic, research in this area has progressed very fast and some mRNA vaccines for COVID-19 are getting emergency use authorization, which means they can now be given to people beyond using them only in clinical trials.
The whole-microbe approach
The first way to make a vaccine is to take the disease-carrying virus or bacterium, or one very similar to it, and inactivate or kill it using chemicals, heat or radiation. This approach uses technology that’s been proven to work in people – this is the way the flu and polio vaccines are made – and vaccines can be manufactured on a reasonable scale.
However, it requires special laboratory facilities to grow the virus or bacterium safely, can have a relatively long production time, and will likely require two or three doses to be administered.
A live-attenuated vaccine uses a living but weakened version of the virus or one that’s very similar.
The measles, mumps and rubella (MMR) vaccine and the chickenpox and shingles vaccine are examples of this type of vaccine. This approach uses similar technology to the inactivated vaccine and can be manufactured at scale. However, vaccines like this may not be suitable for people with compromised immune systems.
Viral vector vaccine
This type of vaccine uses a safe virus to deliver specific sub-parts – called proteins – of the germ of interest so that it can trigger an immune response without causing disease. To do this, the instructions for making particular parts of the pathogen of interest are inserted into a safe virus.
The safe virus then serves as a platform or vector to deliver the protein into the body. The protein triggers the immune response. The Ebola vaccine is a viral vector vaccine and this type can be developed rapidly
The subunit approach
A subunit vaccine is one that only uses the very specific parts (the subunits) of a virus or bacterium that the immune system needs to recognize. It doesn’t contain the whole microbe or use a safe virus as a vector. The subunits may be proteins or sugars. Most of the vaccines on the childhood schedule are subunit vaccines, protecting people from diseases such as whooping cough, tetanus, diphtheria and meningococcal meningitis.
The different types of vaccines
There are three main approaches to designing a vaccine. Their differences lie in whether they use a whole virus or bacterium; just the parts of the germ that triggers the immune system; or just the genetic material that provides the instructions for making specific proteins and not the whole virus.
Types of Covid-19 vaccine:
Up to now several vaccines with different efficacy have been approved by regulatory agencies, including the World Health Organization, the USFDA, and the EMA for emergency use. The Pfizer / BioNTech, Gamaleya, Moderna, Sputnik V and AstraZeneca have 94.5%,92%, 95%, 92% and 70% efficacy, respectively.
Among the inactivated vaccines which get the marketing authorization, Sinopharm (China) shows 79% efficacy in Phase III clinical trial. In addition, the other inactivated vaccine (Sinovac) has shown 50%, 65%, 78% and 91% of effectiveness in different countries. The Bharat Biotech vaccine (India) was studied on 26000 volunteers and approved for use.
Inactivated technology was used for Shifa pharmed Covid-19 vaccine production which steps are summarized as follow:
- Construction of vaccine production site according to international requirements under the supervision of the Iran Food and Drug Administration (IFDA) in 3 months.
- Receiving the code of ethics for animal studies from the National Committee for Research Ethics.
- Preclinical studies on 4 type of animal models including: rats, rabbits, guinea piglets and monkeys.
- Provide necessary documents to the IFDA.
- Production of vaccine in two different doses 3 and 5 μg / ml under the supervision of the IFDA
- Receive the Ethical Code for Clinical Studies from the National Committee for Research Ethics.
- Registration of clinical study in Iranian Registry of Clinical Trials (IRCT).
- Receiving Clinical Batch Release from the Iran Food and Drug Administration.
- Receiving a Clinical Trial Authorization (CTA).
- Starting the Phase I Clinical Trial and Participants enrollment.
- Successful inoculation of the first dose of Covid-19 vaccine in human.
- Continuous monitoring the status of the volunteers apart of performing the necessary tests to evaluate the immunogenicity and adverse events which all conducted by Clinical Trial Center of Tehran University of Medical Sciences (CTC).
- Completion the clinical study and submit a clinical study report to IFDA as well as the National Ethics Committee
- Conducting same mentioned processes for phase II/III clinical trial.
By continuous efforts of virologists, immunologists, microbiologists, chemists, pathologists, pharmacists and the clinical team we hope to reach large scale production of Covid-19 vaccine, in order to improve social health quality.