The shelf life of Covid-19 vaccines

The shelf life of Covid-19 vaccines

Subject – Science and Tech

Context – More than 40 lakh teenagers in the 15-18 age group received their first dose of Covid-19 vaccines on Monday as India began its drive to vaccinate the younger population groups. Some concerns were raised about ‘expired’ Covaxin being administered to this younger group

Concept –

• Shelf life of vaccines is extended by the national regulator, Central Drugs Standard Control Organisation, or CDSCO, based on a comprehensive analysis and examination of stability study data furnished by the vaccine manufacturers.
• Vaccines are complex mixtures of proteins, carbohydrates, lipids, inactivated virus, or adjuvants —which are substances that are intended to enhance immune response and subsequent clinical efficacy of the vaccine. These together contribute to overall vaccine efficacy and safety.
• Like other medicinal products, vaccines come with a date of expiry and shelf life determined by the manufacturer and approved by regulatory authorities. The constituents of a vaccine can go bad over time because of slow chemical reactions and lose efficacy.
• According to the World Health Organization (WHO), stability is the ability of a vaccine to retain its chemical, physical, microbiological and biological properties within specified limits throughout its shelf life.
  • A series of tests are designed to obtain information on the stability of a vaccine in order to define its shelf life and utilisation period under specified packaging and storage conditions.
  • And depending on the nature of the antigen and other components, and the manufacturing process, stability parameters are selected on a case-by-case basis, the WHO guidelines state.

How is shelf life calculated?

• Shelf life is calculated by storing the product at different temperatures for various lengths of time and then testing its effectiveness.
• By storing the particular product at various temperatures, and then periodically checking if there is any degradation of the product, an expiry date is arrived at.
• The duration over which the product is stable and effective in the specified conditions is considered its shelf life.
• 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. The shelf life is used to establish the expiry date of each batch.
• For vaccines, it is done by injecting into small animals (typically mice) to assess if the ability to make antibodies goes down with storage time and temperature.
• An expiry date means that roughly beyond that, the vaccine won’t raise immunity as well as earlier. It may still work but sub-optimally.
• The WHO had said that any extension in the shelf life will only apply to vaccines not yet 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.

Covaxinand Covishield extension –

• CDSCO had in February last year extended the shelf life of Covishield from nine months to 12 months, after a similar process.
• CDSCO on October 25, 2021 approved the extension of the shelf life of covaxin from 9 to 12 months from the date of manufacture.