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Is heat stability of vaccines really possible?

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As a fact, vaccines are required to be stored in a cold environment – temperature ranging from 8 degrees C to 2 degrees C.  Such a fact, sadly, obstructs the path of improving immunization coverage rates.

Another fact pointed out by an international organization of doctors, is that close to one of every five children lacks getting lifesaving vaccinations.

The problem is serious and needs immediate attention. The problem has two solutions:-

  • One solution to the logistic problems faced while keeping vaccines cold is to introduce Heat Stable Vaccines. 
  • Another solution requires leading pharmaceutical companies and research organizations to spread awareness about the importance of storing vaccines in a cold environment.

At present, the scenario requires introducing cold chain right from the time vaccines leave production facility up till the vaccination point. The task is herculean and requires hi-tech, mobile cold storage equipment as well as skilled vaccinologists on the move.

Is it possible to improve the heat stability of vaccines?

Innumerable technologies, as well as processing techniques, are available for improving the heat stability of a vaccine. The major problem, however, lies in the fact that vaccine thermostability varies from product to product. Further, extended thermostability requires immense customization that can burn a hole in the pocket.

Enhancing the stability of vaccines is, however, possible by adopting different processing and stabilization methods. Nevertheless, the end product (after implementing stabilization and processing methods) should be carefully tested as tradeoffs are likely.

In addition, the heat stability of dry vaccines can help them to be re-rendered by using injections. Such a re-rendering process, however, squarely depends on the processing method used for enhancing heat stability.

The dry injectable vaccination, in general, requires reconstitution along with diluents that are used before the first attempt of administration. Reconstitution of dry essential medicines can result in complicating their overall supply chain logistics. 

Which vaccines can have extended thermostability? 

Dry vaccine products have enhanced heat stability when compared with their liquid counterparts. Liquefied presentations of essential medicines can easily get affected by temperature extremes.

Such type of temperature extremes can damage the antigen of essential medicine by doing:-

  • Fluctuations in pH
  • Hydrolysis
  • Aggregation
  • Denaturation
  • Degradation

In addition, temperature extremes can result in causing permanent damage to a vaccine’s potency.

What’s the purpose of having enhanced heat stability? Is it really required?

Enhanced stability allows essential medicines to be used in situations where:-

  • Cold chain systems are either unavailable or unreliable
  • Long shelf life is required for preventing stockpile turnovers (especially for pre-pandemic vaccines)

Technologies and methods to extend the heat stability of a vaccine

A number of research works are undertaken to introduce novel or revamp established methodologies and technologies for enhancing a vaccine’s heat stability.

  • Spray drying – For a long time, the process of spray drying is used for recreating mixes for energy drinks in the food industry. Several leading vaccine research companies have now used the process for extending vaccine’s heat stability. The successful, preclinical development of spray-dried meningococcal has already been done. After successful completion of preclinical, spray-dried meningococcal vaccine, research works are done to develop polysaccharide conjugate vaccine.
  • Foam drying – The process is used to preserve biologics by doing foam formation under controlled temperature and vacuum conditions.
  • Freeze drying – The process helps in developing a dry product by freezing the liquid format of essential medicine. After freezing, the watered particle of an essential medicine can be removed using sublimation (performed under vacuum condition). The process of freeze-drying is also called lyophilization.

To introduce the heat stability of essential medicine, it’s essential that pharmaceutical giants and vaccine research companies join hands and work collectively.

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