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The differences between the COVID-19 Vaccines: From Messenger RNA to Viral Vectors

November 9, 2020

Vaccine Overview:
Messenger RNA compared

There are a lot of different types of vaccines being developed to get us past the COVID-19 pandemic, including GreenLight’s messenger RNA efforts. Here’s our overview of the types of vaccines.

All vaccines strengthen our immune response to infection by introducing a weakened or partial version of a virus.

The ways in which that immune response is provoked varies widely among the five main approaches. Here is our guide.




MESSENGER RNA VACCINES:
How do they work?
Messenger RNA vaccines find and isolate the RNA sequence that codes for a virus’ spike protein. This is introduced into a patient’s cells which then begin to produce the protein, priming the immune system to recognize it.

Strengths
They use low-cost, widely available materials that are easily scaled up and are much faster to produce than traditional vaccines.

Limitations
There are no commercial mRNA vaccines on the market. This means that there are unknowns. Messenger RNA vaccines also require cold storage.

Current Examples
The Pfizer/BioNTech Covid vaccine was approved for use in the UK in December 2020.




ATTENUATED VACCINES:
How do they work?
Attenuated vaccines use a weakened form of the virus that causes a disease.

Strengths
They create a strong and long-lasted immune response.

Limitations
People with weakened immune systems or long-term health problems may not be able to take these types of vaccine.

These vaccines also need to be kept cool, so they don’t travel well.

Current Examples
• Measles, mumps, rubella (MMR Combined vaccine)
• Tuberculosis
• Smallpox
• Chickenpox
• Yellow Fever



KILLED VACCINES:
How do they work?
Killed vaccines use the inactive version of the virus that causes a disease.

Strengths
People with weakened immune systems or long-term health problems will most likely be able to take this type of vaccine.

Limitations
Killed vaccines usually aren’t as strong as attenuated vaccines, and
booster shots may be needed for ongoing immunity.

Current Examples
• Hepatitis A
• Flu (shot only)
• Polio (shot only)
• Rabies




PROTEIN ANTIGEN VACCINES:
How to do they work?
Protein antigen vaccines introduce a small section of the virus (a protein molecule) into the patient, priming the immune system to recognize it.

Strengths
People with weakened immune systems or long-term health problems will most likely be able to take this type of vaccine.

Limitations
Booster shots may be needed for ongoing immunity.

Current Examples
• Hepatitis B
• HPV (Human papillomavirus)
• Whooping cough
• Pneumococcal disease
• Meningococcal disease
• Shingles




VIRAL VECTOR VACCINES:
How do they work?
Viral vector vaccines use the genetic code from the protein of the virus and attach it to another, less virulent virus (often adenovirus). This is then given to the patient, priming the immune system to recognize it.

Strengths
They create a strong immune response.

Limitations:
Booster shots may be needed for ongoing immunity.

Current Examples:
• Hepatitis B
• Cervical cancer
• Malaria