Let's talk vaccines: ᴴᵒʷ ᵃʳᵉ ᵛᵃᶜᶜⁱⁿᵉˢ ᵈᵉᵛᵉˡᵒᵖᵉᵈ?

It starts in a lab, where scientists work to understand a pathogen and figure out how they could trigger the immune system to produce antibodies against it. When they identify a substance they think could work (an antigen), they start by testing it in cell cultures and then animals.

If the vaccine triggers an immune response, it is then tested in human clinical trials in three phases.

Phase 1

The vaccine is given to a small number of volunteers to assess its safety, confirm it generates an immune response, and determine the right dosage. Generally in this phase vaccines are tested in young, healthy adult volunteers.

Phase 2

The vaccine is then given to several hundred volunteers to further assess its safety and ability to generate an immune response. Participants in this phase have the same characteristics (such as age, sex) as the people for whom the vaccine is intended. There are usually multiple trials in this phase to evaluate various age groups and different formulations of the vaccine. A group that did not get the vaccine is usually included in the phase as a comparator group to determine whether the changes in the vaccinated group are attributed to the vaccine, or have happened by chance.

Phase 3

The vaccine is next given to thousands of volunteers – and compared to a similar group of people who didn’t get the vaccine, but received a comparator product – to determine if the vaccine is effective against the disease it is designed to protect against and to study its safety in a much larger group of people. Most of the time phase three trials are conducted across multiple countries and multiple sites within a country to assure the findings of the vaccine performance apply to many different populations.

During phase two and phase three trials, the volunteers and the scientists conducting the study are shielded from knowing which volunteers had received the vaccine being tested or the comparator product. This is called “blinding” and is necessary to assure that neither the volunteers nor the scientists are influenced in their assessment of safety or effectiveness by knowing who got which product.

Once a vaccine has reached the pre-approval stage following clinical trials, it is assessed by the relevant regulatory body for compliance with quality, safety, and efficacy criteria.

Once authorized, manufacturing begins to scale up. The antigen is weakened or deactivated. To form the full vaccine, all ingredients are combined.

Once the vaccine has been made in bulk quantities, it is bottled in glass vials and then carefully packaged for safe cold storage and transport.

Vaccine packaging must be able to withstand extreme temperatures, as well as the risks involved in being transported globally. Therefore, vaccine vials are most commonly made from glass, as it is durable and able to maintain its integrity in extreme temperatures.

When a vaccine is too hot or too cold, it becomes less effective or even inactive. If stored at the incorrect temperature, vaccines can be ruined or unsafe for use. Regular refrigerators cannot maintain an even temperature consistently, so specialized medical refrigerators are required for these precious products.

To maintain this cold chain, vaccines are shipped using specialized equipment that does not compromise the integrity of the product. Once shipments land in the destination country, refrigerated lorries transport the vaccines from the airport to the warehouse cold room. From there, portable iceboxes are used to transport vaccines from the cold room to regional centres where they’re stored in refrigerators. If vaccination takes place outside of the regional facility, the final step often requires portable iceboxes to transport the goods to local areas for vaccination campaigns. New technologies have invented some portable devices that can keep vaccines at their cold temperature for several days without needing electricity.

Once vaccines start being administered, the safety of the vaccine is paramount, with regular assessments and post-approval clinical studies to report on its safety and effectiveness.

{You can find all the sources I used by clicking here.}