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CDC Covid-19 Education Series -4


NOTE: This is part four of a four-part series presented by the WHO. It is excellent and worth sharing.

Manufacturing, Safety, and

Quality Control of Vaccines

Once a vaccine has reached pre-approval stage following clinical trials, it is assessed by the relevant regulatory body for compliance with quality, safety, and efficacy criteria. Following regulatory approval, manufacturers can submit a vaccine to WHO for prequalification (PQ), an assessment process that ensures quality, safety and efficacy and helps the UN and other international procurement organizations determine the programmatic suitability of a vaccine.

During global health emergencies, the WHO Emergency Use Listing Procedure (EUL) may be

used to allow emergency use of the vaccine. The EUL exists because, in a pandemic situation,

products that could benefit the lives of people all over the world may be prevented from coming

to market with sufficient speed. The EUL is a fast-tracked but rigorous process, designed to

bring impactful products to all those in need, as quickly as possible, on a time-limited basis and

based on a risk-versus-benefit evaluation. The WHO PQ/EUL recommendation may be used by

UN agencies such as UNICEF and the Pan American Health Organization Revolving Fund for

Manufacturing, Safety, and Quality Control of Vaccines procurement decisions in low- and middle-income countries. Gavi also relies on WHO EUL/PQ to specify which vaccines its funds may be used to purchase.

How it is made

Typically, companies will work independently to complete clinical development plans for

a vaccine. Once a vaccine is authorized, manufacturing begins to scale up. The antigen

(part of the germ that our immune system reacts to) is weakened or deactivated. To

form the full vaccine, all ingredients are combined.

The whole process, from preclinical trial to manufacture, can sometimes take over a

decade to complete. In the search for a COVID-19 vaccine, researchers and developers

are working on several different phases in parallel, to speed up results. It is the scale of

the financial and political commitments to the development of a vaccine that has

allowed this accelerated development to take place. Also, nations and international

health organizations are working together through COVAX to invest in development

capacity upfront to streamline the process, as well as to ensure equitable distribution of


How it is packaged

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


How it is stored

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. Most

vaccines require refrigerated storage at between 2 and 8 °C. Some vaccines require

temperatures as cold as -20°C. Some of the newer vaccines need to be kept ultra-cold

at -70°C. For frozen vaccines some of them can be safely stored for a limited time

between 2 and 8°C.

Regular refrigerators cannot maintain an even temperature consistently, so specialized

medical refrigerators are required for these precious products.

How it is shipped

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 centers 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.

Quality control

Once vaccines start being administered, national authorities and WHO constantly

monitor for – and establish the severity of – any possible adverse side effects and

responses from people who have received the vaccine. The safety of the vaccine is

paramount, with regular assessments and post-approval clinical studies to report on its

safety and effectiveness.

Studies are often conducted to determine how long a given vaccine remains protective.

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