Vax for teens: Understanding the shelf life of Covid-19 vaccines

Soon after India kickstarted its vaccination drive against Covid-19 for children aged between 15 and 18 years on Monday, many raised concerns over 'expired' Covaxin doses being administered to the age group.

The Centre described such claims as "false and misleading and based on incomplete information". The Health Ministry explained that the Central Drugs Standard Control Organisation (CDSCO) in November had extended the shelf life of these doses from nine to 12 months and that there was nothing wrong with using these batches of vaccine doses. It further added that the shelf life of vaccines is extended by the national regulator after a comprehensive analysis and examination of stability study data furnished by the vaccine manufacturers.

Read more: 41 lakh teenagers got Covid vaccine shots; cumulative doses given in India crosses 146.61 crore

But what is the shelf life of a vaccine and how is it calculated?

According to the WHO guidelines, the shelf life of a vaccine is the period of time during which the vaccine, if stored correctly, is expected to comply with the specification, as determined by stability studies on a number of batches of the product. In simple terms, the shelf life is the duration during which a product can be stored without it becoming unsuitable for use or consumption. Shelf life depends on the degradation mechanism of the specific product. Since all vaccines are made up of proteins, carbohydrates, lipids, inactivated virus, or adjuvants, which degrade with time, even they have a shelf life -- a duration of time till it remains effective and safe.

A vaccine's shelf life is determined by storing it at different temperatures for different lengths of time and testing its effectiveness after that, leading virologist Dr Shahid Jameel is quoted as saying in a report by The Indian Express.

Experts repeat this process (termed as stability study) and check for signs of degradation to conclude a vaccine's expiry date, beyond which it won't be able to maintain the same level of protection it provided before the expiry period. To conduct these stability studies, the maker of a vaccine submits relevant data to get shelf life of jab extended. If the data meets the regulatory standards, as in the case of Covaxin, the expiry date is extended.

“The shelf life of a vaccine is a reflection of how long the vaccine retains its potency and stability at a given storage temperature and therefore its effectiveness. The shelf life is used to establish the expiry date of each batch of the vaccine product. Expiry dates do not affect the safety of the vaccine, rather are related to the potency or amount of protection the vaccine gives,” the WHO regional office for Africa stated in May 2021.

According to the WHO, shelf life extension would apply to only those vaccines that have not yet been labelled and distributed. Hence the expired or near-to-expire doses in distribution for use will not be affected by any future decision of shelf life extension.

Watch the latest DH videos: