Explained: How Shelf Life Of COVID-19 Vaccines Are Determined

BOOM spoke to Dr. Vineeta Bal, immunologist, to understand what determines the shelf life of vaccines and how are they extended

The Ministry of Health and Family Welfare started COVID-19 vaccination for children between the ages of 15-18 on January 3 and has given one dose of Bharat Biotech's Covaxin to over one crore children in this age group. However, this launch faced glitches as several social media users highlighted that the children were given vaccines that were supposed to expire in November and hence would have no effect on the children.

The Health Ministry issued a clarification stating that the Central Drugs Standard Control Organisation, the apex drug body in the country, had extended the shelf life of the vaccine from nine to twelve months in November 2021 after proper regulatory scrutiny. This was not the first time the drug body extended the shelf life of a vaccine. Earlier in February 2021, they had also extended the shelf life of Serum Institute of India's Covishield vaccine from nine months to twelve months.

Shelf life of a vaccine signifies the period till when a vaccine can be administered from the day it was manufactured. Similar to other drugs, vaccines also have an expiry date after which they lose their effectiveness.

BOOM spoke to Dr. Vineeta Bal, immunologist, to understand what determines the shelf life of vaccines and how are they extended.

Determination Of Shelf Life Of Vaccine

Vaccines are made from a mixture of proteins, carbohydrates, lipids, inactivated virus, or adjuvants that enhance the immune response elicited by the ingredients present in the vaccine. Vaccines also have an expiry date like other drugs as the ingredients lose their chemical nature over a period of time.

Dr. Bal told BOOM that based on the guidelines, shelf life of a vaccine is determined by how long the product is stable, and efficacious. "The stability is determined by prolonged storage at various temperatures, and after that physicochemical analysis," the immunologist added.

According to the World Health Organisation, the vaccine has to undergo a series of tests to obtain information on its stability to further define its shelf life and utilisation period under specified packaging and storage conditions. Stability parameters are selected on a case-by-case basis depending on the nature of the antigen the vaccine is acting against, along with its manufacturing process.

The vaccine is stored at different temperatures to check if it is being degraded to determine its stability.

"For efficacy determination, immunogenicity of the vaccine [i.e. ability to trigger immune response] should be checked. Common method will be using experimental animals, mostly mice," Dr. Bal stated. After storing the vaccine at different temperatures, it should be administered to animals to check if it is still providing a similar immune response as earlier.

Dr. Bal also said that the combination of both these features will help in determining the expiry date of the vaccine. Expiry date determined by the shelf-life of the vaccine denotes that the vaccine will generate sub-optimal antibodies against the virus after a certain period of time thus losing its efficacy.

How Is Shelf Life Extended?

The CDSCO had earlier stated that both the Indian vaccines were effective for a period of nine months. Owing to this, all the manufactured vaccine bottles have the date of manufacture and the date of expiry printed on the bottles. This printout caught people's eyes and they questioned the government on social media for putting children at risk

The government responded by stating that this information was false and misleading and that the CDSCO studied the additional details provided by Bharat Biotech. Only after proper regulatory surveillance, they extended the shelf life of the vaccine.

Explaining how shelf life is extended, Dr. Bal used the example of Covaxin's extension. "For emergency use authorisation [EUA] data on stability and efficacy post storage was available for 9 months and hence shelf-life was for 9 months post manufacture. However, between EUA and now batches of vaccines have been tested for longer duration of stability and efficacy [x+y], and turned out to be acceptable by CDSCO. As a result, the shelf-life will have to be extended by 3 months," the immunologist stated.

The extension allows many private players to distribute the vaccine vials that had already reached the earlier expiry date and were supposed to be wasted. Several states earlier reported that many of their Covaxin vials were reaching expiration and thus could not be used.

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